Javascript tutorial

About the Tutorial JavaScript is a lightweight, interpreted programming language. It is designed for creating network-centric applications. It is complimentary to and integrated with Java. JavaScript is very easy to implement because it is integrated with HTML. It is open and cross-platform. Audience This tutorial has been prepared for JavaScript beginners to help them understand the basic functionality of JavaScript to build dynamic web pages and web applications. Prerequisites For this tutorial, it is assumed that the reader have a prior knowledge of HTML coding. It would help if the reader had some prior exposure to object-oriented programming concepts and a general idea on creating online applications. Copyright and Disclaimer  Copyright 2015 by Tutorials Point (I) Pvt. Ltd. All the content and graphics published in this e-book are the property of Tutorials Point (I) Pvt. Ltd. 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If you discover any errors on our website or in this tutorial, please notify us at [email protected] i Table of Contents About the Tutorial ............................................................................................................................................ i Audience ........................................................................................................................................................... i Prerequisites ..................................................................................................................................................... i Copyright and Disclaimer ................................................................................................................................. i Table of Contents ............................................................................................................................................ ii PART 1: JAVASCRIPT BASICS ........................................................................................................ 1 1. Overview .................................................................................................................................................. 2 What is JavaScript? .......................................................................................................................................... 2 Client-Side JavaScript....................................................................................................................................... 2 Advantages of JavaScript ................................................................................................................................. 3 Limitations of JavaScript .................................................................................................................................. 3 JavaScript Development Tools......................................................................................................................... 3 Where is JavaScript Today? ............................................................................................................................. 4 2. Syntax ....................................................................................................................................................... 5 Your First JavaScript Code ............................................................................................................................... 5 Whitespace and Line Breaks ............................................................................................................................ 6 Semicolons are Optional.................................................................................................................................. 6 Case Sensitivity ................................................................................................................................................ 7 Comments in JavaScript .................................................................................................................................. 7 3. Enabling .................................................................................................................................................... 9 JavaScript in Internet Explorer ........................................................................................................................ 9 JavaScript in Firefox ......................................................................................................................................... 9 JavaScript in Chrome ..................................................................................................................................... 10 JavaScript in Opera ........................................................................................................................................ 10 Warning for Non-JavaScript Browsers ........................................................................................................... 10 4. Placement ............................................................................................................................................... 12 JavaScript in <head>...</head> Section ......................................................................................................... 12 JavaScript in <body>...</body> Section ......................................................................................................... 13 JavaScript in <body> and <head> Sections .................................................................................................... 13 JavaScript in External File .............................................................................................................................. 14 5. Variables ................................................................................................................................................. 16 JavaScript Datatypes...................................................................................................................................... 16 JavaScript Variables ....................................................................................................................................... 16 JavaScript Variable Scope .............................................................................................................................. 17 JavaScript Variable Names ............................................................................................................................ 18 JavaScript Reserved Words ........................................................................................................................... 19 6. Operators................................................................................................................................................ 20 What is an Operator? .................................................................................................................................... 20 Arithmetic Operators..................................................................................................................................... 20 Comparison Operators .................................................................................................................................. 23 Logical Operators........................................................................................................................................... 26 ii Bitwise Operators .......................................................................................................................................... 28 Assignment Operators ................................................................................................................................... 31 Miscellaneous Operators............................................................................................................................... 34 7. If-Else ...................................................................................................................................................... 38 Flow Chart of if-else....................................................................................................................................... 38 if Statement ................................................................................................................................................... 39 if...else Statement ......................................................................................................................................... 40 if...else if... Statement ................................................................................................................................... 41 8. Switch-Case............................................................................................................................................. 43 Flow Chart ..................................................................................................................................................... 43 9. While Loop .............................................................................................................................................. 47 The while Loop .............................................................................................................................................. 47 The do...while Loop ....................................................................................................................................... 49 10. For Loop .................................................................................................................................................. 52 The for Loop .................................................................................................................................................. 52 11. For-in Loop .............................................................................................................................................. 55 12. Loop Control ........................................................................................................................................... 57 The break Statement ..................................................................................................................................... 57 The continue Statement ................................................................................................................................ 59 Using Labels to Control the Flow ................................................................................................................... 60 13. Functions ................................................................................................................................................ 64 Function Definition ........................................................................................................................................ 64 Calling a Function .......................................................................................................................................... 65 Function Parameters ..................................................................................................................................... 66 The return Statement .................................................................................................................................... 67 Nested Functions ........................................................................................................................................... 68 Function () Constructor ................................................................................................................................. 70 Function Literals ............................................................................................................................................ 71 14. Events ..................................................................................................................................................... 74 What is an Event? .......................................................................................................................................... 74 onclick Event Type ......................................................................................................................................... 74 onsubmit Event Type ..................................................................................................................................... 75 onmouseover and onmouseout .................................................................................................................... 76 HTML 5 Standard Events ............................................................................................................................... 77 15. Cookies ................................................................................................................................................... 82 What are Cookies?......................................................................................................................................... 82 How It Works? ............................................................................................................................................... 82 Storing Cookies .............................................................................................................................................. 83 Reading Cookies ............................................................................................................................................ 84 Setting Cookies Expiry Date ........................................................................................................................... 86 Deleting a Cookie ........................................................................................................................................... 87 iii 16. Page Redirect .......................................................................................................................................... 89 What is Page Redirection? ............................................................................................................................. 89 JavaScript Page Refresh ................................................................................................................................. 89 Auto Refresh .................................................................................................................................................. 89 How Page Re-direction Works? ..................................................................................................................... 90 17. Dialog Box ............................................................................................................................................... 94 Alert Dialog Box ............................................................................................................................................. 94 Confirmation Dialog Box ................................................................................................................................ 95 Prompt Dialog Box ......................................................................................................................................... 96 18. Void Keyword ......................................................................................................................................... 98 19. Page Printing......................................................................................................................................... 101 How to Print a Page? ................................................................................................................................... 102 PART 2: JAVASCRIPT OBJECTS ................................................................................................. 103 20. Objects.................................................................................................................................................. 105 Object Properties......................................................................................................................................... 105 Object Methods ........................................................................................................................................... 105 User-Defined Objects .................................................................................................................................. 106 Defining Methods for an Object .................................................................................................................. 108 The with Keyword ...................................................................................................................................... 109 21. Number................................................................................................................................................. 111 Number Properties ...................................................................................................................................... 111 MAX_VALUE ................................................................................................................................................ 112 MIN_VALUE ................................................................................................................................................. 113 NaN .............................................................................................................................................................. 114 NEGATIVE_INFINITY ..................................................................................................................................... 116 POSITIVE_INFINITY ...................................................................................................................................... 117 Prototype ..................................................................................................................................................... 118 constructor .................................................................................................................................................. 120 Number Methods ........................................................................................................................................ 120 toExponential () ........................................................................................................................................... 121 toFixed ()...................................................................................................................................................... 123 toLocaleString () .......................................................................................................................................... 124 toPrecision () ............................................................................................................................................... 125 toString () ..................................................................................................................................................... 126 valueOf () ..................................................................................................................................................... 127 22. Boolean ................................................................................................................................................ 129 Boolean Properties ...................................................................................................................................... 129 constructor () ............................................................................................................................................... 129 Prototype ..................................................................................................................................................... 130 Boolean Methods ........................................................................................................................................ 131 toSource () ................................................................................................................................................... 132 toString () ..................................................................................................................................................... 133 valueOf () ..................................................................................................................................................... 134 iv 23. String .................................................................................................................................................... 136 String Properties .......................................................................................................................................... 136 constructor .................................................................................................................................................. 136 Length .......................................................................................................................................................... 137 Prototype ..................................................................................................................................................... 138 String Methods ............................................................................................................................................ 139 charAt() ........................................................................................................................................................ 141 charCodeAt ()............................................................................................................................................... 142 contact () ..................................................................................................................................................... 143 indexOf () ..................................................................................................................................................... 144 lastIndexOf () ............................................................................................................................................... 146 localeCompare () ......................................................................................................................................... 147 match () ....................................................................................................................................................... 148 replace () ...................................................................................................................................................... 149 Search () ....................................................................................................................................................... 152 slice () .......................................................................................................................................................... 153 split () ........................................................................................................................................................... 154 substr ()........................................................................................................................................................ 155 substring () ................................................................................................................................................... 156 toLocaleLowerCase() ................................................................................................................................... 157 toLocaleUppereCase () ................................................................................................................................ 158 toLowerCase ()............................................................................................................................................. 159 toString () ..................................................................................................................................................... 160 toUpperCase () ............................................................................................................................................ 161 valueOf () ..................................................................................................................................................... 162 String HTML Wrappers ................................................................................................................................ 163 anchor() ....................................................................................................................................................... 164 big().............................................................................................................................................................. 165 blink () .......................................................................................................................................................... 166 bold () .......................................................................................................................................................... 166 fixed () .......................................................................................................................................................... 167 fontColor () .................................................................................................................................................. 168 fontsize () ..................................................................................................................................................... 169 italics () ........................................................................................................................................................ 170 link () ............................................................................................................................................................ 171 small () ......................................................................................................................................................... 172 strike ()......................................................................................................................................................... 173 sub() ............................................................................................................................................................. 174 sup () ............................................................................................................................................................ 175 24. Arrays ................................................................................................................................................... 177 Array Properties .......................................................................................................................................... 177 constructor .................................................................................................................................................. 178 length........................................................................................................................................................... 179 Prototype ..................................................................................................................................................... 180 Array Methods ............................................................................................................................................. 181 concat () ....................................................................................................................................................... 183 every ()......................................................................................................................................................... 184 filter () .......................................................................................................................................................... 186 forEach () ..................................................................................................................................................... 189 v indexOf () ..................................................................................................................................................... 191 join () ........................................................................................................................................................... 194 lastIndexOf () ............................................................................................................................................... 195 map () .......................................................................................................................................................... 198 pop () ........................................................................................................................................................... 200 push () .......................................................................................................................................................... 201 reduce () ...................................................................................................................................................... 203 reduceRight () .............................................................................................................................................. 206 reverse () ..................................................................................................................................................... 210 shift () .......................................................................................................................................................... 211 slice () .......................................................................................................................................................... 212 some () ......................................................................................................................................................... 213 sort () ........................................................................................................................................................... 215 splice () ........................................................................................................................................................ 216 toString () ..................................................................................................................................................... 218 unshift () ...................................................................................................................................................... 218 25. Date ...................................................................................................................................................... 220 Date Properties............................................................................................................................................ 221 constructor .................................................................................................................................................. 221 Prototype ..................................................................................................................................................... 222 Date Methods .............................................................................................................................................. 224 Date() ........................................................................................................................................................... 227 getDate()...................................................................................................................................................... 227 getDay() ....................................................................................................................................................... 228 getFullYear() ................................................................................................................................................ 229 getHours() .................................................................................................................................................... 230 getMilliseconds() ......................................................................................................................................... 231 getMinutes () ............................................................................................................................................... 232 getMonth () ................................................................................................................................................. 233 getSeconds () ............................................................................................................................................... 234 getTime () .................................................................................................................................................... 234 getTimezoneOffset () ................................................................................................................................... 235 getUTCDate () .............................................................................................................................................. 236 getUTCDay () ................................................................................................................................................ 237 getUTCFullYear () ......................................................................................................................................... 238 getUTCHours () ............................................................................................................................................ 239 getUTCMilliseconds () .................................................................................................................................. 240 getUTCMinutes () ........................................................................................................................................ 241 getUTCMonth () ........................................................................................................................................... 241 getUTCSeconds () ........................................................................................................................................ 242 getYear () ..................................................................................................................................................... 243 setDate () ..................................................................................................................................................... 244 setFullYear () ................................................................................................................................................ 245 setHours () ................................................................................................................................................... 246 setMilliseconds ()......................................................................................................................................... 247 setMinutes () ............................................................................................................................................... 248 setMonth () .................................................................................................................................................. 249 setSeconds () ............................................................................................................................................... 250 setTime () ..................................................................................................................................................... 252 vi setUTCDate () .............................................................................................................................................. 252 setUTCFullYear () ......................................................................................................................................... 253 setUTCHours () ............................................................................................................................................ 255 setUTCMilliseconds () .................................................................................................................................. 256 setUTCMinutes () ......................................................................................................................................... 257 setUTC Month () .......................................................................................................................................... 258 setUTCSeconds () ......................................................................................................................................... 259 setYear () ..................................................................................................................................................... 260 toDateString () ............................................................................................................................................. 261 toGMTString () ............................................................................................................................................. 262 toLocaleDateString () ................................................................................................................................... 263 toLocaleDateString () ................................................................................................................................... 264 toLocaleFormat () ........................................................................................................................................ 264 toLocaleString () .......................................................................................................................................... 265 toLocaleTimeSring () .................................................................................................................................... 266 toSource () ................................................................................................................................................... 267 toString () ..................................................................................................................................................... 268 toTimeString () ............................................................................................................................................. 269 toUTCString () .............................................................................................................................................. 270 valeOf () ....................................................................................................................................................... 271 Date Static Methods .................................................................................................................................... 272 Date.parse ( ) ............................................................................................................................................... 272 Date.UTC ( ) ................................................................................................................................................. 273 26. Math ..................................................................................................................................................... 275 Math Properties .......................................................................................................................................... 275 Math-E ......................................................................................................................................................... 276 Math-LN2 ..................................................................................................................................................... 277 Math-LN10 ................................................................................................................................................... 277 Math-LOG2E ................................................................................................................................................ 278 Math-LOG10E .............................................................................................................................................. 279 Math-PI ........................................................................................................................................................ 280 Math-SQRT1_2 ............................................................................................................................................ 280 Math-SQRT2 ................................................................................................................................................ 281 Math Methods ............................................................................................................................................. 282 abs () ............................................................................................................................................................ 283 acos () .......................................................................................................................................................... 284 asin ( ) .......................................................................................................................................................... 286 atan ( ) ......................................................................................................................................................... 287 atan2 ( ) ....................................................................................................................................................... 288 ceil ( ) ........................................................................................................................................................... 290 cos ( ) ........................................................................................................................................................... 291 exp ( ) ........................................................................................................................................................... 292 floor ( ) ......................................................................................................................................................... 294 log ( ) ............................................................................................................................................................ 295 max ( ) .......................................................................................................................................................... 296 min ( ) .......................................................................................................................................................... 298 pow ( ).......................................................................................................................................................... 299 random ( ) .................................................................................................................................................... 300 round ( ) ....................................................................................................................................................... 301 vii sin ( ) ............................................................................................................................................................ 303 sqrt ( ) .......................................................................................................................................................... 304 tan ( ) ........................................................................................................................................................... 305 toSource ( ) .................................................................................................................................................. 306 27. RegExp .................................................................................................................................................. 308 Brackets ....................................................................................................................................................... 308 Quantifiers ................................................................................................................................................... 309 Literal Characters......................................................................................................................................... 310 Metacharacters ........................................................................................................................................... 311 Modifiers ..................................................................................................................................................... 311 RegExp Properties ....................................................................................................................................... 312 constructor .................................................................................................................................................. 312 global ........................................................................................................................................................... 313 ignoreCase ................................................................................................................................................... 314 lastIndex ...................................................................................................................................................... 316 multiline....................................................................................................................................................... 317 source .......................................................................................................................................................... 318 RegExp Methods .......................................................................................................................................... 319 exec ( ) ......................................................................................................................................................... 320 test ( ) .......................................................................................................................................................... 321 toSource ( ) .................................................................................................................................................. 322 toString ( ) .................................................................................................................................................... 323 28. DOM ..................................................................................................................................................... 325 The Legacy DOM .......................................................................................................................................... 326 The W3C DOM ............................................................................................................................................. 332 The IE 4 DOM ............................................................................................................................................... 336 DOM Compatibility ...................................................................................................................................... 340 PART 3: JAVASCRIPT ADVANCED ............................................................................................. 342 29. Errors and Exceptions ........................................................................................................................... 343 Syntax Errors................................................................................................................................................ 343 Runtime Errors ............................................................................................................................................ 343 Logical Errors ............................................................................................................................................... 344 The try...catch...finally Statement ............................................................................................................... 344 The throw Statement .................................................................................................................................. 348 The onerror( ) Method ................................................................................................................................ 349 30. Form Validation .................................................................................................................................... 352 Basic Form Validation .................................................................................................................................. 354 Data Format Validation ............................................................................................................................... 355 31. Animation ............................................................................................................................................. 357 Manual Animation ....................................................................................................................................... 358 Automated Animation ................................................................................................................................. 359 Rollover with a Mouse Event ....................................................................................................................... 360 32. Multimedia ........................................................................................................................................... 363 viii Checking for Plug-Ins ................................................................................................................................... 364 Controlling Multimedia ............................................................................................................................... 365 33. Debugging ............................................................................................................................................. 367 Error Messages in IE .................................................................................................................................... 367 Error Messages in Firefox or Mozilla ........................................................................................................... 368 Error Notifications ....................................................................................................................................... 369 How to Debug a Script ................................................................................................................................. 369 Useful Tips for Developers .......................................................................................................................... 370 34. Image Map ............................................................................................................................................ 372 35. Browsers ............................................................................................................................................... 375 Navigator Properties ................................................................................................................................... 375 Navigator Methods ...................................................................................................................................... 376 Browser Detection ....................................................................................................................................... 377 ix Javascript Part 1: JavaScript Basics 1 1. OVERVIEW Javascript What is JavaScript? Javascript is a dynamic computer programming language. It is lightweight and most commonly used as a part of web pages, whose implementations allow client-side script to interact with the user and make dynamic pages. It is an interpreted programming language with object-oriented capabilities. JavaScript was first known as LiveScript, but Netscape changed its name to JavaScript, possibly because of the excitement being generated by Java. JavaScript made its first appearance in Netscape 2.0 in 1995 with the name LiveScript. The general-purpose core of the language has been embedded in Netscape, Internet Explorer, and other web browsers. The ECMA-262 Specification defined a standard version of the core JavaScript language.      JavaScript is a lightweight, interpreted programming language. Designed for creating network-centric applications. Complementary to and integrated with Java. Complementary to and integrated with HTML. Open and cross-platform. Client-Side JavaScript Client-side JavaScript is the most common form of the language. The script should be included in or referenced by an HTML document for the code to be interpreted by the browser. It means that a web page need not be a static HTML, but can include programs that interact with the user, control the browser, and dynamically create HTML content. The JavaScript client-side mechanism provides many advantages over traditional CGI server-side scripts. For example, you might use JavaScript to check if the user has entered a valid e-mail address in a form field. The JavaScript code is executed when the user submits the form, and only if all the entries are valid, they would be submitted to the Web Server. JavaScript can be used to trap user-initiated events such as button clicks, link navigation, and other actions that the user initiates explicitly or implicitly. 2 Javascript Advantages of JavaScript The merits of using JavaScript are:     Less server interaction: You can validate user input before sending the page off to the server. This saves server traffic, which means less load on your server. Immediate feedback to the visitors: They don't have to wait for a page reload to see if they have forgotten to enter something. Increased interactivity: You can create interfaces that react when the user hovers over them with a mouse or activates them via the keyboard. Richer interfaces: You can use JavaScript to include such items as dragand-drop components and sliders to give a Rich Interface to your site visitors. Limitations of JavaScript We cannot treat JavaScript as a full-fledged programming language. It lacks the following important features:    Client-side JavaScript does not allow the reading or writing of files. This has been kept for security reason. JavaScript cannot be used for networking applications because there is no such support available. JavaScript doesn't have any multithreading or multiprocessor capabilities. Once again, JavaScript is a lightweight, interpreted programming language that allows you to build interactivity into otherwise static HTML pages. JavaScript Development Tools One of major strengths of JavaScript is that it does not require expensive development tools. You can start with a simple text editor such as Notepad. Since it is an interpreted language inside the context of a web browser, you don't even need to buy a compiler. To make our life simpler, various vendors have come up with very nice JavaScript editing tools. Some of them are listed here:   Microsoft FrontPage: Microsoft has developed a popular HTML editor called FrontPage. FrontPage also provides web developers with a number of JavaScript tools to assist in the creation of interactive websites. Macromedia Dreamweaver MX: Macromedia Dreamweaver MX is a very popular HTML and JavaScript editor in the professional web development crowd. It provides several handy prebuilt JavaScript 3 Javascript  components, integrates well with databases, and conforms to new standards such as XHTML and XML. Macromedia HomeSite 5: HomeSite 5 is a well-liked HTML and JavaScript editor from Macromedia that can be used to manage personal websites effectively. Where is JavaScript Today? The ECMAScript Edition 5 standard will be the first update to be released in over four years. JavaScript 2.0 conforms to Edition 5 of the ECMAScript standard, and the difference between the two is extremely minor. The specification for JavaScript 2.0 can be found on the following site: http://www.ecmascript.org/ Today, Netscape's JavaScript and Microsoft's JScript conform to the ECMAScript standard, although both the languages still support the features that are not a part of the standard. 4 2. SYNTAX Javascript JavaScript can be implemented using JavaScript statements that are placed within the <script>... </script> HTML tags in a web page. You can place the <script> tags, containing your JavaScript, anywhere within you web page, but it is normally recommended that you should keep it within the <head> tags. The <script> tag alerts the browser program to start interpreting all the text between these tags as a script. A simple syntax of your JavaScript will appear as follows. <script ...> JavaScript code </script> The script tag takes two important attributes:   Language: This attribute specifies what scripting language you are using. Typically, its value will be javascript. Although recent versions of HTML (and XHTML, its successor) have phased out the use of this attribute. Type: This attribute is what is now recommended to indicate the scripting language in use and its value should be set to "text/javascript". So your JavaScript syntax will look as follows. <script language="javascript" type="text/javascript"> JavaScript code </script> Your First JavaScript Code Let us take a sample example to print out "Hello World". We added an optional HTML comment that surrounds our JavaScript code. This is to save our code from a browser that does not support JavaScript. The comment ends with a "//->". Here "//" signifies a comment in JavaScript, so we add that to prevent a browser from reading the end of the HTML comment as a piece of JavaScript code. Next, we call a function document.write which writes a string into our HTML document. 5 Javascript This function can be used to write text, HTML, or both. Take a look at the following code. <html> <body> <script language="javascript" type="text/javascript"> <!-document.write ("Hello World!") //--> </script> </body> </html> This code will produce the following result: Hello World! Whitespace and Line Breaks JavaScript ignores spaces, tabs, and newlines that appear in JavaScript programs. You can use spaces, tabs, and newlines freely in your program and you are free to format and indent your programs in a neat and consistent way that makes the code easy to read and understand. Semicolons are Optional Simple statements in JavaScript are generally followed by a semicolon character, just as they are in C, C++, and Java. JavaScript, however, allows you to omit this semicolon if each of your statements are placed on a separate line. For example, the following code could be written without semicolons. <script language="javascript" type="text/javascript"> <!-var1 = 10 var2 = 20 //--> </script> 6 Javascript But when formatted in a single line as follows, you must use semicolons: <script language="javascript" type="text/javascript"> <!-var1 = 10; var2 = 20; //--> </script> Note: It is a good programming practice to use semicolons. Case Sensitivity JavaScript is a case-sensitive language. This means that the language keywords, variables, function names, and any other identifiers must always be typed with a consistent capitalization of letters. So the identifiers Time and TIME will convey different meanings in JavaScript. NOTE: Care should be taken while writing variable and function names in JavaScript. Comments in JavaScript JavaScript supports both C-style and C++-style comments. Thus:     Any text between a // and the end of a line is treated as a comment and is ignored by JavaScript. Any text between the characters /* and */ is treated as a comment. This may span multiple lines. JavaScript also recognizes the HTML comment opening sequence <!--. JavaScript treats this as a single-line comment, just as it does the // comment. The HTML comment closing sequence --> is not recognized by JavaScript so it should be written as //-->. Example 7 Javascript The following example shows how to use comments in JavaScript. <script language="javascript" type="text/javascript"> <!-- // This is a comment. It is similar to comments in C++ /* * This is a multiline comment in JavaScript * It is very similar to comments in C Programming */ //--> </script> 8 3. ENABLING Javascript All the modern browsers come with built-in support for JavaScript. Frequently, you may need to enable or disable this support manually. This chapter explains the procedure of enabling and disabling JavaScript support in your browsers: Internet Explorer, Firefox, chrome, and Opera. JavaScript in Internet Explorer Here are the steps to turn on or turn off JavaScript in Internet Explorer:       Follow Tools -> Internet Options from the menu. Select Security tab from the dialog box. Click the Custom Level button. Scroll down till you find the Scripting option. Select Enable radio button under Active scripting. Finally click OK and come out. To disable JavaScript support in your Internet Explorer, you need to select Disable radio button under Active scripting. JavaScript in Firefox Here are the steps to turn on or turn off JavaScript in Firefox:      Open a new tab -> type about: config in the address bar. Then you will find the warning dialog. Select I’ll be careful, I promise! Then you will find the list of configure options in the browser. In the search bar, type javascript.enabled. There you will find the option to enable or disable javascript by rightclicking on the value of that option -> select toggle. If javascript.enabled is true; it converts to false upon clicking toogle. If javascript is disabled; it gets enabled upon clicking toggle. 9 Javascript JavaScript in Chrome Here are the steps to turn on or turn off JavaScript in Chrome:  Click the Chrome menu at the top right hand corner of your browser.  Select Settings.  Click Show advanced settings at the end of the page.  Under the Privacy section, click the Content settings button.  In the "Javascript" section, select "Do not allow any site to run JavaScript" or "Allow all sites to run JavaScript (recommended)". JavaScript in Opera Here are the steps to turn on or turn off JavaScript in Opera:  Follow Tools-> Preferences from the menu.  Select Advanced option from the dialog box.  Select Content from the listed items.  Select Enable JavaScript checkbox.  Finally click OK and come out. To disable JavaScript support in Opera, you should not select the Enable JavaScript checkbox. Warning for Non-JavaScript Browsers If you have to do something important using JavaScript, then you can display a warning message to the user using <noscript> tags. You can add a noscript block immediately after the script block as follows: <html> <body> <script language="javascript" type="text/javascript"> <!-document.write ("Hello World!") //--> </script> 10 Javascript <noscript> Sorry...JavaScript is needed to go ahead. </noscript> </body> </html> Now, if the user's browser does not support JavaScript or JavaScript is not enabled, then the message from </noscript> will be displayed on the screen. 11 4. PLACEMENT Javascript There is a flexibility given to include JavaScript code anywhere in an HTML document. However the most preferred ways to include JavaScript in an HTML file are as follows:  Script in <head>...</head> section.  Script in <body>...</body> section.  Script in <body>...</body> and <head>...</head> sections.  Script in an external file and then include in <head>...</head> section. In the following section, we will see how we can place JavaScript in an HTML file in different ways. JavaScript in <head>...</head> Section If you want to have a script run on some event, such as when a user clicks somewhere, then you will place that script in the head as follows. <html> <head> <script type="text/javascript"> <!-function sayHello() { alert("Hello World") } //--> </script> </head> <body> Click here for the result <input type="button" onclick="sayHello()" value="Say Hello" /> </body> </html> 12 Javascript This code will produce the following results: Click here for the result Say Hello JavaScript in <body>...</body> Section If you need a script to run as the page loads so that the script generates content in the page, then the script goes in the <body> portion of the document. In this case, you would not have any function defined using JavaScript. Take a look at the following code. <html> <head> </head> <body> <script type="text/javascript"> <!-document.write("Hello World") //--> </script> <p>This is web page body </p> </body> </html> This code will produce the following results: Hello World This is web page body JavaScript in <body> and <head> Sections You can put your JavaScript code in <head> and <body> section altogether as follows. <html> <head> <script type="text/javascript"> 13 Javascript <!-function sayHello() { alert("Hello World") } //--> </script> </head> <body> <script type="text/javascript"> <!-document.write("Hello World") //--> </script> <input type="button" onclick="sayHello()" value="Say Hello" /> </body> </html> This code will produce the following result. HelloWorld Say Hello JavaScript in External File As you begin to work more extensively with JavaScript, you will be likely to find that there are cases where you are reusing identical JavaScript code on multiple pages of a site. You are not restricted to be maintaining identical code in multiple HTML files. The script tag provides a mechanism to allow you to store JavaScript in an external file and then include it into your HTML files. Here is an example to show how you can include an external JavaScript file in your HTML code using script tag and its src attribute. 14 Javascript <html> <head> <script type="text/javascript" src="filename.js" ></script> </head> <body> ....... </body> </html> To use JavaScript from an external file source, you need to write all your JavaScript source code in a simple text file with the extension ".js" and then include that file as shown above. For example, you can keep the following content in filename.js file and then you can use sayHello function in your HTML file after including the filename.js file. function sayHello() { alert("Hello World") } 15 5. VARIABLES Javascript JavaScript Datatypes One of the most fundamental characteristics of a programming language is the set of data types it supports. These are the type of values that can be represented and manipulated in a programming language. JavaScript allows you to work with three primitive data types:    Numbers, e.g., 123, 120.50 etc. Strings of text, e.g. "This text string" etc. Boolean, e.g. true or false. JavaScript also defines two trivial data types, null and undefined, each of which defines only a single value. In addition to these primitive data types, JavaScript supports a composite data type known as object. We will cover objects in detail in a separate chapter. Note: Java does not make a distinction between integer values and floatingpoint values. All numbers in JavaScript are represented as floating-point values. JavaScript represents numbers using the 64-bit floating-point format defined by the IEEE 754 standard. JavaScript Variables Like many other programming languages, JavaScript has variables. Variables can be thought of as named containers. You can place data into these containers and then refer to the data simply by naming the container. Before you use a variable in a JavaScript program, you must declare it. Variables are declared with the var keyword as follows. <script type="text/javascript"> <!-var money; var name; //--> </script> 16 Javascript You can also declare multiple variables with the same var keyword as follows: <script type="text/javascript"> <!-var money, name; //--> </script> Storing a value in a variable is called variable initialization. You can do variable initialization at the time of variable creation or at a later point in time when you need that variable. For instance, you might create a variable named money and assign the value 2000.50 to it later. For another variable, you can assign a value at the time of initialization as follows. <script type="text/javascript"> <!-var name = "Ali"; var money; money = 2000.50; //--> </script> Note: Use the var keyword only for declaration or initialization, once for the life of any variable name in a document. You should not re-declare same variable twice. JavaScript is untyped language. This means that a JavaScript variable can hold a value of any data type. Unlike many other languages, you don't have to tell JavaScript during variable declaration what type of value the variable will hold. The value type of a variable can change during the execution of a program and JavaScript takes care of it automatically. JavaScript Variable Scope The scope of a variable is the region of your program in which it is defined. JavaScript variables have only two scopes.   Global Variables: A global variable has global scope which means it can be defined anywhere in your JavaScript code. Local Variables: A local variable will be visible only within a function where it is defined. Function parameters are always local to that function. 17 Javascript Within the body of a function, a local variable takes precedence over a global variable with the same name. If you declare a local variable or function parameter with the same name as a global variable, you effectively hide the global variable. Take a look into the following example. <script type="text/javascript"> <!-var myVar = "global"; // Declare a global variable function checkscope( ) { var myVar = "local"; // Declare a local variable document.write(myVar); } //--> </script> It will produce the following result: Local JavaScript Variable Names While naming your variables in JavaScript, keep the following rules in mind.    You should not use any of the JavaScript reserved keywords as a variable name. These keywords are mentioned in the next section. For example, break or boolean variable names are not valid. JavaScript variable names should not start with a numeral (0-9). They must begin with a letter or an underscore character. For example, 123test is an invalid variable name but _123test is a valid one. JavaScript variable names are case-sensitive. For example, Name and name are two different variables. 18 Javascript JavaScript Reserved Words A list of all the reserved words in JavaScript are given in the following table. They cannot be used as JavaScript variables, functions, methods, loop labels, or any object names. abstract else Instanceof switch boolean enum int synchronized break export interface this byte extends long throw case false native throws catch final new transient char finally null true class float package try const for private typeof continue function protected var debugger goto public void default if return volatile delete implements short while do import static with double in super 19 6. OPERATORS Javascript What is an Operator? Let us take a simple expression 4 + 5 is equal to 9. Here 4 and 5 are called operands and ‘+’ is called the operator. JavaScript supports the following types of operators.      Arithmetic Operators Comparison Operators Logical (or Relational) Operators Assignment Operators Conditional (or ternary) Operators Let’s have a look at all the operators one by one. Arithmetic Operators JavaScript supports the following arithmetic operators: Assume variable A holds 10 and variable B holds 20, then: S. No. Operator and Description + (Addition) 1 Adds two operands Ex: A + B will give 30 - (Subtraction) 2 Subtracts the second operand from the first Ex: A - B will give -10 * (Multiplication) 3 Multiply both operands Ex: A * B will give 200 4 / (Division) 20 Javascript Divide the numerator by the denominator Ex: B / A will give 2 % (Modulus) 5 Outputs the remainder of an integer division Ex: B % A will give 0 ++ (Increment) 6 Increases an integer value by one Ex: A++ will give 11 -- (Decrement) 7 Decreases an integer value by one Ex: A-- will give 9 Note: Addition operator (+) works for Numeric as well as Strings. e.g. "a" + 10 will give "a10". Example The following code shows how to use arithmetic operators in JavaScript. <html> <body> <script type="text/javascript"> <!-var a = 33; var b = 10; var c = "Test"; var linebreak = "<br />"; document.write("a + b = "); result = a + b; document.write(result); document.write(linebreak); 21 Javascript document.write("a - b = "); result = a - b; document.write(result); document.write(linebreak); document.write("a / b = "); result = a / b; document.write(result); document.write(linebreak); document.write("a % b = "); result = a % b; document.write(result); document.write(linebreak); document.write("a + b + c = "); result = a + b + c; document.write(result); document.write(linebreak); a = a++; document.write("a++ = "); result = a++; document.write(result); document.write(linebreak); b = b--; document.write("b-- = "); result = b--; document.write(result); document.write(linebreak); 22 Javascript //--> </script> <p>Set the variables to different values and then try...</p> </body> </html> Output a + a a / a % a + a++ b-- b b b b b = = = 43 = 23 = 3.3 = 3 + c = 43Test 33 10 Set the variables to different values and then try... Comparison Operators JavaScript supports the following comparison operators: Assume variable A holds 10 and variable B holds 20, then: S.No Operator and Description == (Equal) 1 Checks if the value of two operands are equal or not, if yes, then the condition becomes true. Ex: (A == B) is not true. != (Not Equal) 2 Checks if the value of two operands are equal or not, if the values are not equal, then the condition becomes true. Ex: (A != B) is true. 3 > (Greater than) Checks if the value of the left operand is greater than the value of 23 Javascript the right operand, if yes, then the condition becomes true. Ex: (A > B) is not true. < (Less than) 4 Checks if the value of the left operand is less than the value of the right operand, if yes, then the condition becomes true. Ex: (A < B) is true. >= (Greater than or Equal to) 5 Checks if the value of the left operand is greater than or equal to the value of the right operand, if yes, then the condition becomes true. Ex: (A >= B) is not true. <= (Less than or Equal to) 6 Checks if the value of the left operand is less than or equal to the value of the right operand, if yes, then the condition becomes true. Ex: (A <= B) is true. Example The following code shows how to use comparison operators in JavaScript. <html> <body> <script type="text/javascript"> <!-var a = 10; var b = 20; var linebreak = "<br />"; document.write("(a == b) => "); result = (a == b); document.write(result); document.write(linebreak); 24 Javascript document.write("(a < b) => "); result = (a < b); document.write(result); document.write(linebreak); document.write("(a > b) => "); result = (a > b); document.write(result); document.write(linebreak); document.write("(a != b) => "); result = (a != b); document.write(result); document.write(linebreak); document.write("(a >= b) => "); result = (a >= b); document.write(result); document.write(linebreak); document.write("(a <= b) => "); result = (a <= b); document.write(result); document.write(linebreak); //--> </script> <p>Set the variables to different values and different operators and then try...</p> </body> </html> 25 Javascript Output (a (a (a (a (a (a == b) => false < b) => true > b) => false != b) => true >= b) => false <= b) => true Set the variables to different values and different operators and then try... Logical Operators JavaScript supports the following logical operators: Assume variable A holds 10 and variable B holds 20, then: S.No Operator and Description && (Logical AND) 1 If both the operands are non-zero, then the condition becomes true. Ex: (A && B) is true. || (Logical OR) 2 If any of the two operands are non-zero, then the condition becomes true. Ex: (A || B) is true. ! (Logical NOT) 3 Reverses the logical state of its operand. If a condition is true, then the Logical NOT operator will make it false. Ex: ! (A && B) is false. Example 26 Javascript Try the following code to learn how to implement Logical Operators in JavaScript. <html> <body> <script type="text/javascript"> <!-var a = true; var b = false; var linebreak = "<br />"; document.write("(a && b) => "); result = (a && b); document.write(result); document.write(linebreak); document.write("(a || b) => "); result = (a || b); document.write(result); document.write(linebreak); document.write("!(a && b) => "); result = (!(a && b)); document.write(result); document.write(linebreak); //--> </script> <p>Set the variables to different values and different operators and then try...</p> 27 Javascript </body> </html> Output (a && b) => false (a || b) => true !(a && b) => true Set the variables to different values and different operators and then try... Bitwise Operators JavaScript supports the following bitwise operators: Assume variable A holds 2 and variable B holds 3, then: S.No Operator and Description & (Bitwise AND) 1 It performs a Boolean AND operation on each bit of its integer arguments. Ex: (A & B) is 2. | (BitWise OR) 2 It performs a Boolean OR operation on each bit of its integer arguments. Ex: (A | B) is 3. ^ (Bitwise XOR) 3 It performs a Boolean exclusive OR operation on each bit of its integer arguments. Exclusive OR means that either operand one is true or operand two is true, but not both. Ex: (A ^ B) is 1. ~ (Bitwise Not) 4 It is a unary operator and operates by reversing all the bits in the operand. 28 Javascript Ex: (~B) is -4. << (Left Shift) 5 It moves all the bits in its first operand to the left by the number of places specified in the second operand. New bits are filled with zeros. Shifting a value left by one position is equivalent to multiplying it by 2, shifting two positions is equivalent to multiplying by 4, and so on. Ex: (A << 1) is 4. >> (Right Shift) 6 Binary Right Shift Operator. The left operand’s value is moved right by the number of bits specified by the right operand. Ex: (A >> 1) is 1. >>> (Right shift with Zero) 7 This operator is just like the >> operator, except that the bits shifted in on the left are always zero. Ex: (A >>> 1) is 1. Example Try the following code to implement Bitwise operator in JavaScript. <html> <body> <script type="text/javascript"> <!-var a = 2; // Bit presentation 10 var b = 3; // Bit presentation 11 var linebreak = "<br />"; document.write("(a & b) => "); result = (a & b); document.write(result); document.write(linebreak); 29 Javascript document.write("(a | b) => "); result = (a | b); document.write(result); document.write(linebreak); document.write("(a ^ b) => "); result = (a ^ b); document.write(result); document.write(linebreak); document.write("(~b) => "); result = (~b); document.write(result); document.write(linebreak); document.write("(a << b) => "); result = (a << b); document.write(result); document.write(linebreak); document.write("(a >> b) => "); result = (a >> b); document.write(result); document.write(linebreak); //--> </script> <p>Set the variables to different values and different operators and then try...</p> </body> </html> Output 30 Javascript (a & b) => 2 (a | b) => 3 (a ^ b) => 1 (~b) => -4 (a << b) => 16 (a >> b) => 0 Set the variables to different values and different operators and then try... Assignment Operators JavaScript supports the following assignment operators: S.No Operator and Description = (Simple Assignment ) 1 Assigns values from the right side operand to the left side operand Ex: C = A + B will assign the value of A + B into C += (Add and Assignment) 2 It adds the right operand to the left operand and assigns the result to the left operand. Ex: C += A is equivalent to C = C + A -= (Subtract and Assignment) 3 It subtracts the right operand from the left operand and assigns the result to the left operand. Ex: C -= A is equivalent to C = C - A *= (Multiply and Assignment) 4 It multiplies the right operand with the left operand and assigns the result to the left operand. Ex: C *= A is equivalent to C = C * A /= (Divide and Assignment) 5 It divides the left operand with the right operand and assigns the result to the left operand. 31 Javascript Ex: C /= A is equivalent to C = C / A %= (Modules and Assignment) 6 It takes modulus using two operands and assigns the result to the left operand. Ex: C %= A is equivalent to C = C % A Note: Same logic applies to Bitwise operators, so they will become <<=, >>=, >>=, &=, |= and ^=. Example Try the following code to implement assignment operator in JavaScript. <html> <body> <script type="text/javascript"> <!-var a = 33; var b = 10; var linebreak = "<br />"; document.write("Value of a => (a = b) => "); result = (a = b); document.write(result); document.write(linebreak); document.write("Value of a => (a += b) => "); result = (a += b); document.write(result); document.write(linebreak); document.write("Value of a => (a -= b) => "); result = (a -= b); document.write(result); 32 Javascript document.write(linebreak); document.write("Value of a => (a *= b) => "); result = (a *= b); document.write(result); document.write(linebreak); document.write("Value of a => (a /= b) => "); result = (a /= b); document.write(result); document.write(linebreak); document.write("Value of a => (a %= b) => "); result = (a %= b); document.write(result); document.write(linebreak); //--> </script> <p>Set the variables to different values and different operators and then try...</p> </body> </html> Output Value Value Value Value Value Value of of of of of of a a a a a a => => => => => => (a (a (a (a (a (a = b) => 10 += b) => 20 -= b) => 10 *= b) => 100 /= b) => 10 %= b) => 0 33 Javascript Set the variables to different values and different operators and then try... Miscellaneous Operators We will discuss two operators here that are quite useful in JavaScript: the conditional operator (? :) and the typeof operator. Conditional Operator (? :) The conditional operator first evaluates an expression for a true or false value and then executes one of the two given statements depending upon the result of the evaluation. S.No 1 Operator and Description ? : (Conditional ) If Condition is true? Then value X : Otherwise value Y Example Try the following code to understand how the Conditional Operator works in JavaScript. <html> <body> <script type="text/javascript"> <!-var a = 10; var b = 20; var linebreak = "<br />"; document.write ("((a > b) ? 100 : 200) => "); result = (a > b) ? 100 : 200; document.write(result); document.write(linebreak); document.write ("((a < b) ? 100 : 200) => "); 34 Javascript result = (a < b) ? 100 : 200; document.write(result); document.write(linebreak); //--> </script> <p>Set the variables to different values and different operators and then try...</p> </body> </html> Output ((a > b) ? 100 : 200) => 200 ((a < b) ? 100 : 200) => 100 Set the variables to different values and different operators and then try... typeof Operator The typeof operator is a unary operator that is placed before its single operand, which can be of any type. Its value is a string indicating the data type of the operand. The typeof operator evaluates to "number", "string", or "boolean" if its operand is a number, string, or boolean value and returns true or false based on the evaluation. Here is a list of the return values for the typeof Operator. Type String Returned by typeof Number "number" String "string" Boolean "boolean" Object "object" 35 Javascript Function "function" Undefined "undefined" Null "object" Example The following code shows how to implement typeof operator. <html> <body> <script type="text/javascript"> <!-var a = 10; var b = "String"; var linebreak = "<br />"; result = (typeof b == "string" ? "B is String" : "B is Numeric"); document.write("Result => "); document.write(result); document.write(linebreak); result = (typeof a == "string" ? "A is String" : "A is Numeric"); document.write("Result => "); document.write(result); document.write(linebreak); //--> </script> <p>Set the variables to different values and different operators and then try...</p> </body> </html> 36 Javascript Output Result => B is String Result => A is Numeric Set the variables to different values and different operators and then try... 37 7. IF-ELSE Javascript While writing a program, there may be a situation when you need to adopt one out of a given set of paths. In such cases, you need to use conditional statements that allow your program to make correct decisions and perform right actions. JavaScript supports conditional statements which are used to perform different actions based on different conditions. Here we will explain the if..else statement. Flow Chart of if-else The following flow chart shows how the if-else statement works. JavaScript supports the following forms of if..else statement:    if statement if...else statement if...else if... statement 38 Javascript if Statement The ‘if’ statement is the fundamental control statement that allows JavaScript to make decisions and execute statements conditionally. Syntax The syntax for a basic if statement is as follows: if (expression){ Statement(s) to be executed if expression is true } Here a JavaScript expression is evaluated. If the resulting value is true, the given statement(s) are executed. If the expression is false, then no statement would be not executed. Most of the times, you will use comparison operators while making decisions. Example Try the following example to understand how the if statement works. <html> <body> <script type="text/javascript"> <!-var age = 20; if( age > 18 ){ document.write("<b>Qualifies for driving</b>"); } //--> </script> <p>Set the variable to different value and then try...</p> </body> </html> 39 Javascript Output Qualifies for driving Set the variable to different value and then try... if...else Statement The ‘if...else’ statement is the next form of control statement that allows JavaScript to execute statements in a more controlled way. Syntax The syntax of an if-else statement is as follows: if (expression){ Statement(s) to be executed if expression is true }else{ Statement(s) to be executed if expression is false } Here JavaScript expression is evaluated. If the resulting value is true, the given statement(s) in the ‘if’ block, are executed. If the expression is false, then the given statement(s) in the else block are executed. Example Try the following code to learn how to implement an if-else statement in JavaScript. <html> <body> <script type="text/javascript"> <!-var age = 15; if( age > 18 ){ document.write("<b>Qualifies for driving</b>"); }else{ document.write("<b>Does not qualify for driving</b>"); } 40 Javascript //--> </script> <p>Set the variable to different value and then try...</p> </body> </html> Output Does not qualify for driving Set the variable to different value and then try... if...else if... Statement The ‘if...else if...’ statement is an advanced form of if…else that allows JavaScript to make a correct decision out of several conditions. Syntax The syntax of an if-else-if statement is as follows: if (expression 1){ Statement(s) to be executed if expression 1 is true }else if (expression 2){ Statement(s) to be executed if expression 2 is true }else if (expression 3){ Statement(s) to be executed if expression 3 is true }else{ Statement(s) to be executed if no expression is true } There is nothing special about this code. It is just a series of if statements, where each if is a part of the else clause of the previous statement. Statement(s) are executed based on the true condition, if none of the conditions is true, then the else block is executed. Example 41 Javascript Try the following code to learn how to implement an if-else-if statement in JavaScript. <html> <body> <script type="text/javascript"> <!-var book = "maths"; if( book == "history" ){ document.write("<b>History Book</b>"); }else if( book == "maths" ){ document.write("<b>Maths Book</b>"); }else if( book == "economics" ){ document.write("<b>Economics Book</b>"); }else{ document.write("<b>Unknown Book</b>"); } //--> </script> <p>Set the variable to different value and then try...</p> </body> </html> Output Maths Book Set the variable to different value and then try... 42 8. SWITCH-CASE Javascript You can use multiple if...else…if statements, as in the previous chapter, to perform a multiway branch. However, this is not always the best solution, especially when all of the branches depend on the value of a single variable. Starting with JavaScript 1.2, you can use a switch statement which handles exactly this situation, and it does so more efficiently than repeated if...else if statements. Flow Chart The following flow chart explains a switch-case statement works. 43 Javascript Syntax The objective of a switch statement is to give an expression to evaluate and several different statements to execute based on the value of the expression. The interpreter checks each case against the value of the expression until a match is found. If nothing matches, a default condition will be used. switch (expression) { case condition 1: statement(s) break; case condition 2: statement(s) break; ... case condition n: statement(s) break; default: statement(s) } The break statements indicate the end of a particular case. If they were omitted, the interpreter would continue executing each statement in each of the following cases. We will explain break statement in Loop Control chapter. Example Try the following example to implement switch-case statement. <html> <body> <script type="text/javascript"> <!-var grade='A'; document.write("Entering switch block<br />"); switch (grade) { case 'A': document.write("Good job<br />"); 44 Javascript break; case 'B': document.write("Pretty good<br />"); break; case 'C': document.write("Passed<br />"); break; case 'D': document.write("Not so good<br />"); break; case 'F': document.write("Failed<br />"); break; default: document.write("Unknown grade<br />") } document.write("Exiting switch block"); //--> </script> <p>Set the variable to different value and then try...</p> </body> </html> Output Entering switch block Good job Exiting switch block Set the variable to different value and then try... Break statements play a major role in switch-case statements. Try the following code that uses switch-case statement without any break statement. <html> <body> <script type="text/javascript"> <!-var grade='A'; document.write("Entering switch block<br />"); 45 Javascript switch (grade) { case 'A': document.write("Good job<br />"); case 'B': document.write("Pretty good<br />"); case 'C': document.write("Passed<br />"); case 'D': document.write("Not so good<br />"); case 'F': document.write("Failed<br />"); default: document.write("Unknown grade<br />") } document.write("Exiting switch block"); //--> </script> <p>Set the variable to different value and then try...</p> </body> </html> Output Entering switch block Good job Pretty good Passed Not so good Failed Unknown grade Exiting switch block Set the variable to different value and then try... 46 9. WHILE LOOP Javascript While writing a program, you may encounter a situation where you need to perform an action over and over again. In such situations, you would need to write loop statements to reduce the number of lines. JavaScript supports all the necessary loops to ease down the pressure of programming. The while Loop The most basic loop in JavaScript is the while loop which would be discussed in this chapter. The purpose of a while loop is to execute a statement or code block repeatedly as long as an expression is true. Once the expression becomes false, the loop terminates. Flow Chart The flow chart of while loop looks as follows: 47 Javascript Syntax The syntax of while loop in JavaScript is as follows: while (expression){ Statement(s) to be executed if expression is true } Example Try the following example to implement while loop. <html> <body> <script type="text/javascript"> <!-var count = 0; document.write("Starting Loop "); while (count < 10){ document.write("Current Count : " + count + "<br />"); count++; } document.write("Loop stopped!"); //--> </script> <p>Set the variable to different value and then try...</p> </body> </html> Output Starting Loop Current Count Current Count Current Count Current Count Current Count : 0 : 1 : 2 : 3 : 4 48 Javascript Current Count Current Count Current Count Current Count Current Count Loop stopped! : : : : : 5 6 7 8 9 Set the variable to different value and then try... The do...while Loop The do...while loop is similar to the while loop except that the condition check happens at the end of the loop. This means that the loop will always be executed at least once, even if the condition is false. Flow Chart The flow chart of a do-while loop would be as follows: do{ conditional code; }while(condition); Conditional Code Condition If condition is true If Condition is false Syntax The syntax for do-while loop in JavaScript is as follows: 49 Javascript do{ Statement(s) to be executed; } while (expression); Note: Don’t miss the semicolon used at the end of the do...while loop. Example Try the following example to learn how to implement a do-while loop in JavaScript. <html> <body> <script type="text/javascript"> <!-var count = 0; document.write("Starting Loop" + "<br />"); do{ document.write("Current Count : " + count + "<br />"); count++; }while (count < 5); document.write ("Loop stopped!"); //--> </script> <p>Set the variable to different value and then try...</p> </body> </html> Output Starting Loop Current Current Current Current Current Count Count Count Count Count : : : : : 0 1 2 3 4 Loop Stopped! 50 Javascript Set the variable to different value and then try... 51 10. FOR LOOP Javascript The for Loop The ‘for’ loop is the most compact form of looping. It includes the following three important parts:    The loop initialization where we initialize our counter to a starting value. The initialization statement is executed before the loop begins. The test statement which will test if a given condition is true or not. If the condition is true, then the code given inside the loop will be executed, otherwise the control will come out of the loop. The iteration statement where you can increase or decrease your counter. You can put all the three parts in a single line separated by semicolons. Flow Chart The flow chart of a for loop in JavaScript would be as follows: Conditional Code Condition for condition is true for Condition is false 52 Javascript Syntax The syntax of for loop is JavaScript is as follows: for (initialization; test condition; iteration statement){ Statement(s) to be executed if test condition is true } Example Try the following example to learn how a for loop works in JavaScript. <html> <body> <script type="text/javascript"> <!-var count; document.write("Starting Loop" + "<br />"); for(count = 0; count < 10; count++){ document.write("Current Count : " + count ); document.write("<br />"); } document.write("Loop stopped!"); //--> </script> <p>Set the variable to different value and then try...</p> </body> </html> Output Starting Loop Current Count Current Count Current Count Current Count Current Count Current Count : : : : : : 0 1 2 3 4 5 53 Javascript Current Count Current Count Current Count Current Count Loop stopped! : : : : 6 7 8 9 Set the variable to different value and then try... 54 11. FOR-IN LOOP Javascript The for...in loop is used to loop through an object's properties. As we have not discussed Objects yet, you may not feel comfortable with this loop. But once you understand how objects behave in JavaScript, you will find this loop very useful. Syntax The syntax of ‘for..in’ loop is: for (variablename in object){ statement or block to execute } In each iteration, one property from object is assigned to variablename and this loop continues till all the properties of the object are exhausted. Example Try the following example to implement ‘for-in’ loop. It prints the web browser’s Navigator object. <html> <body> <script type="text/javascript"> <!-var aProperty; document.write("Navigator Object Properties<br /> "); for (aProperty in navigator) { document.write(aProperty); document.write("<br />"); } document.write ("Exiting from the loop!"); //--> </script> 55 Javascript <p>Set the variable to different object and then try...</p> </body> </html> Output Navigator Object Properties serviceWorker webkitPersistentStorage webkitTemporaryStorage geolocation doNotTrack onLine languages language userAgent product platform appVersion appName appCodeName hardwareConcurrency maxTouchPoints vendorSub vendor productSub cookieEnabled mimeTypes plugins javaEnabled getStorageUpdates getGamepads webkitGetUserMedia vibrate getBattery sendBeacon registerProtocolHandler unregisterProtocolHandler Exiting from the loop! Set the variable to different object and then try... 56 12. LOOP CONTROL Javascript JavaScript provides full control to handle loops and switch statements. There may be a situation when you need to come out of a loop without reaching at its bottom. There may also be a situation when you want to skip a part of your code block and start the next iteration of the look. To handle all such situations, JavaScript provides break and continue statements. These statements are used to immediately come out of any loop or to start the next iteration of any loop respectively. The break Statement The break statement, which was briefly introduced with the switch statement, is used to exit a loop early, breaking out of the enclosing curly braces. Flow Chart The flow chart of a break statement would look as follows: Condition true Conditional Code Break statement false Example The following example illustrates the use of a break statement with a while loop. Notice how the loop breaks out early once x reaches 5 and reaches to document.write (..) statement just below to the closing curly brace: 57 Javascript <html> <body> <script type="text/javascript"> <!-var x = 1; document.write("Entering the loop<br /> "); while (x < 20) { if (x == 5){ break; // breaks out of loop completely } x = x + 1; document.write( x + "<br />"); } document.write("Exiting the loop!<br /> "); //--> </script> <p>Set the variable to different value and then try...</p> </body> </html> Output Entering the loop 2 3 4 5 Exiting the loop! Set the variable to different value and then try... We have already seen the usage of break statement inside a switch statement. 58 Javascript The continue Statement The continue statement tells the interpreter to immediately start the next iteration of the loop and skip the remaining code block. When a continue statement is encountered, the program flow moves to the loop check expression immediately and if the condition remains true, then it starts the next iteration, otherwise the control comes out of the loop. Example This example illustrates the use of a continue statement with a while loop. Notice how the continue statement is used to skip printing when the index held in variable x reaches 5. <html> <body> <script type="text/javascript"> <!-var x = 1; document.write("Entering the loop<br /> "); while (x < 10) { x = x + 1; if (x == 5){ continue; // skill rest of the loop body } document.write( x + "<br />"); } document.write("Exiting the loop!<br /> "); //--> </script> <p>Set the variable to different value and then try...</p> </body> </html> Output 59 Javascript Entering the loop 2 3 4 6 7 8 9 10 Exiting the loop! Using Labels to Control the Flow Starting from JavaScript 1.2, a label can be used with break and continue to control the flow more precisely. A label is simply an identifier followed by a colon (:) that is applied to a statement or a block of code. We will see two different examples to understand how to use labels with break and continue. Note: Line breaks are not allowed between the ‘continue’ or ‘break’ statement and its label name. Also, there should not be any other statement in between a label name and associated loop. Try the following two examples for a better understanding of Labels. Example 1 The following example shows how to implement Label with a break statement. <html> <body> <script type="text/javascript"> <!-document.write("Entering the loop!<br /> "); outerloop: // This is the label name for (var i = 0; i < 5; i++) { document.write("Outerloop: " + i + "<br />"); innerloop: for (var j = 0; j < 5; j++) 60 Javascript { if (j > 3 ) break ; // Quit the innermost loop if (i == 2) break innerloop; // Do the same thing if (i == 4) break outerloop; // Quit the outer loop document.write("Innerloop: " + j + " <br />"); } } document.write("Exiting the loop!<br /> "); //--> </script> </body> </html> Output Entering the loop! Outerloop: 0 Innerloop: 0 Innerloop: 1 Innerloop: 2 Innerloop: 3 Outerloop: 1 Innerloop: 0 Innerloop: 1 Innerloop: 2 Innerloop: 3 Outerloop: 2 Outerloop: 3 Innerloop: 0 Innerloop: 1 Innerloop: 2 Innerloop: 3 Outerloop: 4 Exiting the loop! Example 2 The following example shows how to implement Label with continue. <html> 61 Javascript <body> <script type="text/javascript"> <!-document.write("Entering the loop!<br /> "); outerloop: // This is the label name for (var i = 0; i < 3; i++) { document.write("Outerloop: " + i + "<br />"); for (var j = 0; j < 5; j++) { if (j == 3){ continue outerloop; } document.write("Innerloop: " + j + "<br />"); } } document.write("Exiting the loop!<br /> "); //--> </script> </body> </html> Output Entering the loop! Outerloop: 0 Innerloop: 0 Innerloop: 1 Innerloop: 2 Outerloop: 1 Innerloop: 0 Innerloop: 1 Innerloop: 2 Outerloop: 2 Innerloop: 0 Innerloop: 1 62 Javascript Innerloop: 2 Exiting the loop! 63 13. FUNCTIONS Javascript A function is a group of reusable code which can be called anywhere in your program. This eliminates the need of writing the same code again and again. It helps programmers in writing modular codes. Functions allow a programmer to divide a big program into a number of small and manageable functions. Like any other advanced programming language, JavaScript also supports all the features necessary to write modular code using functions. You must have seen functions like alert() and write() in the earlier chapters. We were using these functions again and again, but they had been written in core JavaScript only once. JavaScript allows us to write our own functions as well. This section explains how to write your own functions in JavaScript. Function Definition Before we use a function, we need to define it. The most common way to define a function in JavaScript is by using the function keyword, followed by a unique function name, a list of parameters (that might be empty), and a statement block surrounded by curly braces. Syntax The basic syntax is shown here. <script type="text/javascript"> <!-function functionname(parameter-list) { statements } //--> </script> Example Try the following example. It defines a function called sayHello that takes no parameters: 64 Javascript <script type="text/javascript"> <!-function sayHello() { alert("Hello there"); } //--> </script> Calling a Function To invoke a function somewhere later in the script, you would simply need to write the name of that function as shown in the following code. <html> <head> <script type="text/javascript"> function sayHello() { document.write ("Hello there!"); } </script> </head> <body> <p>Click the following button to call the function</p> <form> <input type="button" onclick="sayHello()" value="Say Hello"> </form> <p>Use different text in write method and then try...</p> </body> </html> Output 65 Javascript Click the following button to call the function Say Hello Function Parameters Till now, we have seen functions without parameters. But there is a facility to pass different parameters while calling a function. These passed parameters can be captured inside the function and any manipulation can be done over those parameters. A function can take multiple parameters separated by comma. Example Try the following example. We have modified our sayHello function here. Now it takes two parameters. <html> <head> <script type="text/javascript"> function sayHello(name, age) { document.write (name + " is " + age + " years old."); } </script> </head> <body> <p>Click the following button to call the function</p> <form> <input type="button" onclick="sayHello('Zara', 7)" value="Say Hello"> </form> <p>Use different parameters inside the function and then try...</p> </body> </html> 66 Javascript Output Click the following button to call the function Say Hello Use different parameters inside the function and then try... The return Statement A JavaScript function can have an optional return statement. This is required if you want to return a value from a function. This statement should be the last statement in a function. For example, you can pass two numbers in a function and then you can expect the function to return their multiplication in your calling program. Example Try the following example. It defines a function that takes two parameters and concatenates them before returning the resultant in the calling program. <html> <head> <script type="text/javascript"> function concatenate(first, last) { var full; full = first + last; return full; } function secondFunction() { var result; result = concatenate('Zara', 'Ali'); document.write (result ); } </script> </head> 67 Javascript <body> <p>Click the following button to call the function</p> <form> <input type="button" onclick="secondFunction()" value="Call Function"> </form> <p>Use different parameters inside the function and then try...</p> </body> </html> Output Click the following button to call the function Call Function Use different parameters inside the function and then try... There is a lot to learn about JavaScript functions, however we have covered the most important concepts in this tutorial. Nested Functions Prior to JavaScript 1.2, function definition was allowed only in top level global code, but JavaScript 1.2 allows function definitions to be nested within other functions as well. Still there is a restriction that function definitions may not appear within loops or conditionals. These restrictions on function definitions apply only to function declarations with the function statement. As we'll discuss later in the next chapter, function literals (another feature introduced in JavaScript 1.2) may appear within any JavaScript expression, which means that they can appear within if and other statements. Example Try the following example to learn how to implement nested functions. <html> 68 Javascript <head> <script type="text/javascript"> <!-function hypotenuse(a, b) { function square(x) { return x*x; } return Math.sqrt(square(a) + square(b)); } function secondFunction(){ var result; result = hypotenuse(1,2); document.write ( result ); } //--> </script> </head> <body> <p>Click the following button to call the function</p> <form> <input type="button" onclick="secondFunction()" value="Call Function"> </form> <p>Use different parameters inside the function and then try...</p> </body> </html> Output Click the following button to call the function Call Function 69 Javascript Use different parameters inside the function and then try... Function () Constructor The function statement is not the only way to define a new function; you can define your function dynamically using Function() constructor along with the new operator. Note: Constructor is a terminology from Object Oriented Programming. You may not feel comfortable for the first time, which is OK. Syntax Following is the syntax to create a function using Function() constructor along with the new operator. <script type="text/javascript"> <!-var variablename = new Function(Arg1, Arg2..., "Function Body"); //--> </script> The Function() constructor expects any number of string arguments. The last argument is the body of the function – it can contain arbitrary JavaScript statements, separated from each other by semicolons. Notice that the Function() constructor is not passed any argument that specifies a name for the function it creates. The unnamed functions created with the Function() constructor are called anonymous functions. Example Try the following example. <html> <head> <script type="text/javascript"> <!-var func = new Function("x", "y", "return x*y;"); function secondFunction(){ var result; result = func(10,20); 70 Javascript document.write ( result ); } //--> </script> </head> <body> <p>Click the following button to call the function</p> <form> <input type="button" onclick="secondFunction()" value="Call Function"> </form> <p>Use different parameters inside the function and then try...</p> </body> </html> Output Click the following button to call the function Call Function Use different parameters inside the function and then try... Function Literals JavaScript 1.2 introduces the concept of function literals which is another new way of defining functions. A function literal is an expression that defines an unnamed function. Syntax The syntax for a function literal is much like a function statement, except that it is used as an expression rather than a statement and no function name is required. <script type="text/javascript"> <!-71 Javascript var variablename = function(Argument List){ Function Body }; //--> </script> Syntactically, you can specify a function name while creating a literal function as follows. <script type="text/javascript"> <!-var variablename = function FunctionName(Argument List){ Function Body }; //--> </script> But this name does not have any significance, so it is not worthwhile. Example Try the following example. It shows the usage of function literals. <html> <head> <script type="text/javascript"> <!-var func = function(x,y){ return x*y }; function secondFunction(){ var result; result = func(10,20); document.write ( result ); } //--> </script> </head> <body> 72 Javascript <p>Click the following button to call the function</p> <form> <input type="button" onclick="secondFunction()" value="Call Function"> </form> <p>Use different parameters inside the function and then try...</p> </body> </html> Output Click the following button to call the function Call Function Use different parameters inside the function and then try... 73 14. EVENTS Javascript What is an Event? JavaScript's interaction with HTML is handled through events that occur when the user or the browser manipulates a page. When the page loads, it is called an event. When the user clicks a button, that click too is an event. Other examples include events like pressing any key, closing a window, resizing a window, etc. Developers can use these events to execute JavaScript coded responses, which cause buttons to close windows, messages to be displayed to users, data to be validated, and virtually any other type of response imaginable. Events are a part of the Document Object Model (DOM) Level 3 and every HTML element contains a set of events which can trigger JavaScript Code. Please go through this small tutorial for a better understanding HTML Event Reference. Here we will see a few examples to understand the relation between Event and JavaScript. onclick Event Type This is the most frequently used event type which occurs when a user clicks the left button of his mouse. You can put your validation, warning etc., against this event type. Example Try the following example. <html> <head> <script type="text/javascript"> <!-function sayHello() { document.write ("Hello World") } //--> </script> 74 Javascript </head> <body> <p> Click the following button and see result</p> <input type="button" onclick="sayHello()" value="Say Hello" /> </body> </html> Output Click the following button and see result Say Hello onsubmit Event Type onsubmit is an event that occurs when you try to submit a form. You can put your form validation against this event type. Example The following example shows how to use onsubmit. Here we are calling a validate() function before submitting a form data to the webserver. If validate() function returns true, the form will be submitted, otherwise it will not submit the data. Try the following example. <html> <head> <script type="text/javascript"> <!-function validation() { all validation goes here ......... return either true or false } //--> </script> </head> 75 Javascript <body> <form method="POST" action="t.cgi" onsubmit="return validate()"> ....... <input type="submit" value="Submit" /> </form> </body> </html> onmouseover and onmouseout These two event types will help you create nice effects with images or even with text as well. The onmouseover event triggers when you bring your mouse over any element and the onmouseout triggers when you move your mouse out from that element. Try the following example. <html> <head> <script type="text/javascript"> <!-function over() { document.write ("Mouse Over"); } function out() { document.write ("Mouse Out"); } //--> </script> </head> <body> <p>Bring your mouse inside the division to see the result:</p> <div onmouseover="over()" onmouseout="out()"> <h2> This is inside the division </h2> </div> </body> </html> 76 Javascript Output Bring your mouse inside the division to see the result: This is inside the division HTML 5 Standard Events The standard HTML 5 events are listed here for your reference. Here script indicates a Javascript function to be executed against that event. Attribute Value Description Offline script Triggers when the document goes offline Onabort script Triggers on an abort event onafterprint script Triggers after the document is printed onbeforeonload script Triggers before the document loads onbeforeprint script Triggers before the document is printed onblur script Triggers when the window loses focus oncanplay script Triggers when media can start play, but might has to stop for buffering oncanplaythrough script Triggers when media can be played to the end, without stopping for buffering onchange script Triggers when an element changes onclick script Triggers on a mouse click oncontextmenu script Triggers when a context menu is triggered ondblclick script Triggers on a mouse double-click ondrag script Triggers when an element is dragged ondragend script Triggers at the end of a drag operation 77 Javascript ondragenter script Triggers when an element has been dragged to a valid drop target ondragleave script Triggers when an element leaves a valid drop target ondragover script Triggers when an element is being dragged over a valid drop target ondragstart script Triggers at the start of a drag operation ondrop script Triggers when dragged element is being dropped ondurationchange script Triggers when the length of the media is changed onemptied script Triggers when a media resource element suddenly becomes empty. onended script Triggers when media has reach the end onerror script Triggers when an error occur onfocus script Triggers when the window gets focus onformchange script Triggers when a form changes onforminput script Triggers when a form gets user input onhaschange script Triggers when the document has change oninput script Triggers when an element gets user input oninvalid script Triggers when an element is invalid onkeydown script Triggers when a key is pressed onkeypress script Triggers when a key is pressed and released onkeyup script Triggers when a key is released 78 Javascript onload script Triggers when the document loads onloadeddata script Triggers when media data is loaded onloadedmetadata script Triggers when the duration and other media data of a media element is loaded onloadstart script Triggers when the browser starts to load the media data onmessage script Triggers when the message is triggered onmousedown script Triggers when a mouse button is pressed onmousemove script Triggers when the mouse pointer moves onmouseout script Triggers when the mouse pointer moves out of an element onmouseover script Triggers when the mouse pointer moves over an element onmouseup script Triggers when a mouse button is released onmousewheel script Triggers when the mouse wheel is being rotated onoffline script Triggers when the document goes offline onoine script Triggers when the document comes online ononline script Triggers when the document comes online onpagehide script Triggers when the window is hidden onpageshow script Triggers when the window becomes visible onpause script Triggers when media data is paused onplay script Triggers when media data is going to start playing 79 Javascript onplaying script Triggers when media data has start playing onpopstate script Triggers when the window's history changes onprogress script Triggers when the browser is fetching the media data onratechange script Triggers when the media data's playing rate has changed onreadystatechange script Triggers when the ready-state changes onredo script Triggers when the document performs a redo onresize script Triggers when the window is resized onscroll script Triggers when an element's scrollbar is being scrolled onseeked script Triggers when a media element's seeking attribute is no longer true, and the seeking has ended onseeking script Triggers when a media element's seeking attribute is true, and the seeking has begun onselect script Triggers when an element is selected onstalled script Triggers when there is an error in fetching media data onstorage script Triggers when a document loads onsubmit script Triggers when a form is submitted onsuspend script Triggers when the browser has been fetching media data, but stopped before the entire media file was fetched ontimeupdate script Triggers when media changes its playing position onundo script Triggers when a document performs an undo 80 Javascript onunload script Triggers when the user leaves the document onvolumechange script Triggers when media changes the volume, also when volume is set to "mute" onwaiting script Triggers when media has stopped playing, but is expected to resume 81 15. COOKIES Javascript What are Cookies? Web Browsers and Servers use HTTP protocol to communicate and HTTP is a stateless protocol. But for a commercial website, it is required to maintain session information among different pages. For example, one user registration ends after completing many pages. But how to maintain users' session information across all the web pages. In many situations, using cookies is the most efficient method of remembering and tracking preferences, purchases, commissions, and other information required for better visitor experience or site statistics. How It Works? Your server sends some data to the visitor's browser in the form of a cookie. The browser may accept the cookie. If it does, it is stored as a plain text record on the visitor's hard drive. Now, when the visitor arrives at another page on your site, the browser sends the same cookie to the server for retrieval. Once retrieved, your server knows/remembers what was stored earlier. Cookies are a plain text data record of 5 variable-length fields:      Expires: The date the cookie will expire. If this is blank, the cookie will expire when the visitor quits the browser. Domain: The domain name of your site. Path: The path to the directory or web page that set the cookie. This may be blank if you want to retrieve the cookie from any directory or page. Secure: If this field contains the word "secure", then the cookie may only be retrieved with a secure server. If this field is blank, no such restriction exists. Name=Value: Cookies are set and retrieved in the form of key-value pairs. Cookies were originally designed for CGI programming. The data contained in a cookie is automatically transmitted between the web browser and the web server, so CGI scripts on the server can read and write cookie values that are stored on the client. 82 Javascript JavaScript can also manipulate cookies using the cookie property of the Document object. JavaScript can read, create, modify, and delete the cookies that apply to the current web page. Storing Cookies The simplest way to create a cookie is to assign a string value to the document.cookie object, which looks like this. document.cookie = "key1=value1;key2=value2;expires=date"; Here the expires attribute is optional. If you provide this attribute with a valid date or time, then the cookie will expire on a given date or time and thereafter, the cookies' value will not be accessible. Note: Cookie values may not include semicolons, commas, or whitespace. For this reason, you may want to use the JavaScript escape() function to encode the value before storing it in the cookie. If you do this, you will also have to use the corresponding unescape() function when you read the cookie value. Example Try the following. It sets a customer name in an input cookie. <html> <head> <script type="text/javascript"> <!-function WriteCookie() { if( document.myform.customer.value == "" ){ alert ("Enter some value!"); return; } cookievalue= escape(document.myform.customer.value) + ";"; document.cookie="name=" + cookievalue; document.write ("Setting Cookies : " + "name=" + cookievalue ); } //--> </script> 83 Javascript </head> <body> <form name="myform" action=""> Enter name: <input type="text" name="customer"/> <input type="button" value="Set Cookie" onclick="WriteCookie();"/> </form> </body> </html> Output Enter name: Set Cookie Now your machine has a cookie called name. You can set multiple cookies using multiple key=value pairs separated by comma. Reading Cookies Reading a cookie is just as simple as writing one, because the value of the document.cookie object is the cookie. So you can use this string whenever you want to access the cookie. The document.cookie string will keep a list of name=value pairs separated by semicolons, where name is the name of a cookie and value is its string value. You can use strings' split() function to break a string into key and values as follows: Example Try the following example to get all the cookies. <html> <head> <script type="text/javascript"> <!-function ReadCookie() { var allcookies = document.cookie; document.write ("All Cookies : " + allcookies ); 84 Javascript // Get all the cookies pairs in an array cookiearray = allcookies.split(';'); // Now take key value pair out of this array for(var i=0; i<cookiearray.length; i++){ name = cookiearray[i].split('=')[0]; value = cookiearray[i].split('=')[1]; document.write ("Key is : " + name + " and Value is : " + value); } } //--> </script> </head> <body> <form name="myform" action=""> <p> click the following button and see the result:</p> <input type="button" value="Get Cookie" onclick="ReadCookie()"/> </form> </body> </html> Note: Here length is a method of Array class which returns the length of an array. We will discuss Arrays in a separate chapter. By that time, please try to digest it. Output click the following button and see the result: Get Cookie Note: There may be some other cookies already set on your machine. The above code will display all the cookies set on your machine. 85 Javascript Setting Cookies Expiry Date You can extend the life of a cookie beyond the current browser session by setting an expiration date and saving the expiry date within the cookie. This can be done by setting the ‘expires’ attribute to a date and time. Example Try the following example. It illustrates how to extend the expiry date of a cookie by 1 Month. <html> <head> <script type="text/javascript"> <!-function WriteCookie() { var now = new Date(); now.setMonth( now.getMonth() + 1 ); cookievalue = escape(document.myform.customer.value) + ";" document.cookie="name=" + cookievalue; document.cookie = "expires=" + now.toUTCString() + ";" document.write ("Setting Cookies : " + "name=" + cookievalue ); } //--> </script> </head> <body> <form name="formname" action=""> Enter name: <input type="text" name="customer"/> <input type="button" value="Set Cookie" onclick="WriteCookie()"/> </form> </body> </html> 86 Javascript Output Enter Cookie Name: Set Cookie Deleting a Cookie Sometimes you will want to delete a cookie so that subsequent attempts to read the cookie return nothing. To do this, you just need to set the expiry date to a time in the past. Example Try the following example. It illustrates how to delete a cookie by setting its expiry date to one month behind the current date. <html> <head> <script type="text/javascript"> <!-function WriteCookie() { var now = new Date(); now.setMonth( now.getMonth() - 1 ); cookievalue = escape(document.myform.customer.value) + ";" document.cookie="name=" + cookievalue; document.cookie = "expires=" + now.toUTCString() + ";" document.write("Setting Cookies : " + "name=" + cookievalue ); } //--> </script> </head> <body> <form name="formname" action=""> Enter name: <input type="text" name="customer"/> <input type="button" value="Set Cookie" onclick="WriteCookie()"/> </form> 87 Javascript </body> </html> Output Set Cookie Enter Cookie Name: 88 16. PAGE REDIRECT Javascript What is Page Redirection? You might have encountered a situation where you clicked a URL to reach a page X but internally you were directed to another page Y. It happens due to page redirection. This concept is different from JavaScript Page Refresh. There could be various reasons why you would like to redirect a user from the original page. We are listing down a few of the reasons:    You did not like the name of your domain and you are moving to a new one. In such a scenario, you may want to direct all your visitors to the new site. Here you can maintain your old domain but put a single page with a page redirection such that all your old domain visitors can come to your new domain. You have built-up various pages based on browser versions or their names or may be based on different countries, then instead of using your server-side page redirection, you can use client-side page redirection to land your users on the appropriate page. The Search Engines may have already indexed your pages. But while moving to another domain, you would not like to lose your visitors coming through search engines. So you can use client-side page redirection. But keep in mind this should not be done to fool the search engine, it could lead your site to get banned. JavaScript Page Refresh You can refresh a web page using JavaScript location.reload method. This code can be called automatically upon an event or simply when the user clicks on a link. If you want to refresh a web page using a mouse click, then you can use the following code: <a href="javascript:location.reload(true)">Refresh Page</a> Auto Refresh You can also use JavaScript to refresh the page automatically after a given time period. Here setTimeout() is a built-in JavaScript function which can be used to execute another function after a given time interval. 89 Javascript Example Try the following example. It shows how to refresh a page after every 5 seconds. You can change this time as per your requirement. <html> <head> <script type="text/JavaScript"> <!-function AutoRefresh( t ) { setTimeout("location.reload(true);", t); } // --> </script> </head> <body onload="JavaScript:AutoRefresh(5000);"> <p>This page will refresh every 5 seconds.</p> </body> </html> Output This page will refresh every 5 seconds. How Page Re-direction Works? The implementations of Page-Redirection are as follows. Example 1 It is quite simple to do a page redirect using JavaScript at client side. To redirect your site visitors to a new page, you just need to add a line in your head section as follows. <html> <head> <script type="text/javascript"> <!-function Redirect() { 90 Javascript window.location="http://www.tutorialspoint.com"; } //--> </script> </head> <body> <p>Click the following button, you will be redirected to home page.</p> <form> <input type="button" value="Redirect Me" onclick="Redirect();" /> </form> </body> </html> Output Click the following button, you will be redirected to home page. Redirect Me Example 2 You can show an appropriate message to your site visitors before redirecting them to a new page. This would need a bit time delay to load a new page. The following example shows how to implement the same. Here setTimeout() is a built-in JavaScript function which can be used to execute another function after a given time interval. <html> <head> <script type="text/javascript"> <!-function Redirect() { window.location="http://www.tutorialspoint.com"; } document.write ("You will be redirected to our main page in 10 seconds!"); 91 Javascript setTimeout('Redirect()', 10000); //--> </script> </head> <body> </body> </html> Output You will be redirected to tutorialspoint.com main page in 10 seconds! Example 3 The following example shows how to redirect your site visitors onto a different page based on their browsers. <html> <head> <script type="text/javascript"> <!-var browsername=navigator.appName; if( browsername == "Netscape" ) { window.location="http://www.location.com/ns.htm"; } else if ( browsername =="Microsoft Internet Explorer") { window.location="http://www.location.com/ie.htm"; } else { window.location="http://www.location.com/other.htm"; } //--> </script> 92 Javascript </head> <body> </body> </html> 93 17. DIALOG BOX Javascript JavaScript supports three important types of dialog boxes. These dialog boxes can be used to raise and alert, or to get confirmation on any input or to have a kind of input from the users. Here we will discuss each dialog box one by one. Alert Dialog Box An alert dialog box is mostly used to give a warning message to the users. For example, if one input field requires to enter some text but the user does not provide any input, then as a part of validation, you can use an alert box to give a warning message. Nonetheless, an alert box can still be used for friendlier messages. Alert box gives only one button "OK" to select and proceed. Example <html> <head> <script type="text/javascript"> <!-function Warn() { alert ("This is a warning message!"); document.write ("This is a warning message!"); } //--> </script> </head> <body> <p>Click the following button to see the result: </p> <form> <input type="button" value="Click Me" onclick="Warn();" /> </form> </body> </html> 94 Javascript Output Click the following button to see the result: Click Me Confirmation Dialog Box A confirmation dialog box is mostly used to take user's consent on any option. It displays a dialog box with two buttons: OK and Cancel. If the user clicks on the OK button, the window method confirm() will return true. If the user clicks on the Cancel button, then confirm() returns false. You can use a confirmation dialog box as follows. Example <html> <head> <script type="text/javascript"> <!-function getConfirmation(){ var retVal = confirm("Do you want to continue ?"); if( retVal == true ){ document.write ("User wants to continue!"); return true; }else{ Document.write ("User does not want to continue!"); return false; } } //--> </script> </head> <body> <p>Click the following button to see the result: </p> <form> 95 Javascript <input type="button" value="Click Me" onclick="getConfirmation();" /> </form> </body> </html> Output Click the following button to see the result: Click Me Prompt Dialog Box The prompt dialog box is very useful when you want to pop-up a text box to get user input. Thus, it enables you to interact with the user. The user needs to fill in the field and then click OK. This dialog box is displayed using a method called prompt() which takes two parameters: (i) a label which you want to display in the text box and (ii) a default string to display in the text box. This dialog box has two buttons: OK and Cancel. If the user clicks the OK button, the window method prompt() will return the entered value from the text box. If the user clicks the Cancel button, the window method prompt() returns null. Example The following example shows how to use a prompt dialog box: <html> <head> <script type="text/javascript"> <!-function getValue(){ var retVal = prompt("Enter your name : ", "your name here"); document.write("You have entered : " + retVal); } //--> 96 Javascript </script> </head> <body> <p>Click the following button to see the result: </p> <form> <input type="button" value="Click Me" onclick="getValue();" /> </form> </body> </html> Output Click the following button to see the result: Click Me 97 18. VOID KEYWORD Javascript void is an important keyword in JavaScript which can be used as a unary operator that appears before its single operand, which may be of any type. This operator specifies an expression to be evaluated without returning a value. Syntax The syntax of void can be either of the following two: <head> <script type="text/javascript"> <!-void func() javascript:void func() OR void(func()) javascript:void(func()) //--> </script> </head> Example 1 The most common use of this operator is in a client-side javascript: URL, where it allows you to evaluate an expression for its side-effects without the browser displaying the value of the evaluated expression. Here the expression alert ('Warning!!!') is evaluated but it is not loaded back into the current document: <html> <head> <script type="text/javascript"> <!-//--> </script> </head> 98 Javascript <body> <p>Click the following, This won't react at all...</p> <a href="javascript:void document.write Hello : 0 ">Click me!</a> </body> </html> Output Click the following, This won't react at all... Click me! Example 2 Take a look at the following example. The following link does nothing because the expression "0" has no effect in JavaScript. Here the expression "0" is evaluated, but it is not loaded back into the current document. <html> <head> <script type="text/javascript"> <!-//--> </script> </head> <body> <p>Click the following, This won't react at all...</p> <a href="javascript:void(0)">Click me!</a> </body> </html> Output Click the following, This won't react at all... Click me! Example 3 Another use of void is to purposely generate the undefined value as follows. <html> 99 Javascript <head> <script type="text/javascript"> <!-function getValue(){ var a,b,c; a = void ( b = 5, c = 7 ); document.write('a = ' + a + ' b = ' + b +' c = ' + c ); } //--> </script> </head> <body> <p>Click the following to see the result:</p> <form> <input type="button" value="Click Me" onclick="getValue();" /> </body> </html> Output Click the following button to see the result: Click Me 100 19. PAGE PRINTING Javascript Many times you would like to place a button on your webpage to print the content of that web page via an actual printer. JavaScript helps you to implement this functionality using the print function of window object. The JavaScript print function window.print() prints the current web page when executed. You can call this function directly using the onclick event as shown in the following example. Example Try the following example. <head> <script type="text/javascript"> <!-//--> </script> </head> <body> <form> <input type="button" value="Print" onclick="window.print()" /> </form> </body> Output Print Although it serves the purpose of getting a printout, it is not a recommended way. A printer friendly page is really just a page with text, no images, graphics, or advertising. You can make a page printer friendly in the following ways: 1. Make a copy of the page and leave out unwanted text and graphics, then link to that printer friendly page from the original. Check Example. 101 Javascript 2. If you do not want to keep an extra copy of a page, then you can mark your printable text using proper comments like <!-- PRINT STARTS HERE -->..... <!-- PRINT ENDS HERE --> and then you can use PERL or any other script in the background to purge printable text and display for final printing. We at Tutorialspoint use this method to provide print facility to our site visitors. Check Example. How to Print a Page? If you don’t find the above facilities on a web page, then you can use the browser's standard toolbar to get print the web page. Follow the link as follows. File --> Print --> Click OK button. 102 Javascript Part 2: JavaScript Objects 103 Javascript 104 20. OBJECTS Javascript JavaScript is an Object Oriented Programming (OOP) language. A programming language can be called object-oriented if it provides four basic capabilities to developers:     Encapsulation: the capability to store related information, whether data or methods, together in an object. Aggregation: the capability to store one object inside another object. Inheritance: the capability of a class to rely upon another class (or number of classes) for some of its properties and methods. Polymorphism: the capability to write one function or method that works in a variety of different ways. Objects are composed of attributes. If an attribute contains a function, it is considered to be a method of the object, otherwise the attribute is considered a property. Object Properties Object properties can be any of the three primitive data types, or any of the abstract data types, such as another object. Object properties are usually variables that are used internally in the object's methods, but can also be globally visible variables that are used throughout the page. The syntax for adding a property to an object is: objectName.objectProperty = propertyValue; For example: The following code gets the document title using the "title" property of the document object. var str = document.title; Object Methods Methods are the functions that let the object do something or let something be done to it. There is a small difference between a function and a method – at a function is a standalone unit of statements and a method is attached to an object and can be referenced by the this keyword. 105 Javascript Methods are useful for everything from displaying the contents of the object to the screen to performing complex mathematical operations on a group of local properties and parameters. For example: Following is a simple example to show how to use the write() method of document object to write any content on the document. document.write ("This is test"); User-Defined Objects All user-defined objects and built-in objects are descendants of an object called Object. The new Operator The new operator is used to create an instance of an object. To create an object, the new operator is followed by the constructor method. In the following example, the constructor methods are Object(), Array(), and Date(). These constructors are built-in JavaScript functions. var employee = new Object(); var books = new Array("C++", "Perl", "Java"); var day = new Date("August 15, 1947"); The Object ( ) Constructor A constructor is a function that creates and initializes an object. JavaScript provides a special constructor function called Object() to build the object. The return value of the Object() constructor is assigned to a variable. The variable contains a reference to the new object. The properties assigned to the object are not variables and are not defined with the var keyword. Example 1 Try the following example; it demonstrates how to create an Object. <html> <head> <title>User-defined objects</title> <script type="text/javascript"> var book = new Object(); // Create the object book.subject = "Perl"; // Assign properties to the object 106 Javascript book.author = "Mohtashim"; </script> </head> <body> <script type="text/javascript"> document.write("Book name is : " + book.subject + "<br>"); document.write("Book author is : " + book.author + "<br>"); </script> </body> </html> Output Book name is : Perl Book author is : Mohtashim Example 2 This example demonstrates how to create an object with a User-Defined Function. Here this keyword is used to refer to the object that has been passed to a function. <html> <head> <title>User-defined objects</title> <script type="text/javascript"> function book(title, author){ this.title = title; this.author = author; } </script> </head> <body> <script type="text/javascript"> var myBook = new book("Perl", "Mohtashim"); document.write("Book title is : " + myBook.title + "<br>"); document.write("Book author is : " + myBook.author + "<br>"); 107 Javascript </script> </body> </html> Output Book title is : Perl Book author is : Mohtashim Defining Methods for an Object The previous examples demonstrate how the constructor creates the object and assigns properties. But we need to complete the definition of an object by assigning methods to it. Example Try the following example; it shows how to add a function along with an object. <html> <head> <title>User-defined objects</title> <script type="text/javascript"> // Define a function which will work as a method function addPrice(amount){ this.price = amount; } function book(title, author){ this.title = title; this.author = author; this.addPrice = addPrice; // Assign that method as property. } </script> </head> <body> 108 Javascript <script type="text/javascript"> var myBook = new book("Perl", "Mohtashim"); myBook.addPrice(100); document.write("Book title is : " + myBook.title + "<br>"); document.write("Book author is : " + myBook.author + "<br>"); document.write("Book price is : " + myBook.price + "<br>"); </script> </body> </html> Output Book title is : Perl Book author is : Mohtashim Book price is : 100 The ‘with’ Keyword The ‘with’ keyword is used as a kind of shorthand for referencing an object's properties or methods. The object specified as an argument to with becomes the default object for the duration of the block that follows. The properties and methods for the object can be used without naming the object. Syntax The syntax for with object is as follows: with (object){ properties used without the object name and dot } Example Try the following example. <html> 109 Javascript <head> <title>User-defined objects</title> <script type="text/javascript"> // Define a function which will work as a method function addPrice(amount){ with(this){ price = amount; } } function book(title, author){ this.title = title; this.author = author; this.price = 0; this.addPrice = addPrice; // Assign that method as property. } </script> </head> <body> <script type="text/javascript"> var myBook = new book("Perl", "Mohtashim"); myBook.addPrice(100); document.write("Book title is : " + myBook.title + "<br>"); document.write("Book author is : " + myBook.author + "<br>"); document.write("Book price is : " + myBook.price + "<br>"); </script> </body> </html> Output Book title is : Perl Book author is : Mohtashim Book price is : 100 110 21. NUMBER Javascript The Number object represents numerical date, either integers or floating-point numbers. In general, you do not need to worry about Number objects because the browser automatically converts number literals to instances of the number class. Syntax The syntax for creating a number object is as follows: var val = new Number(number); In the place of number, if you provide any non-number argument, then the argument cannot be converted into a number, it returns NaN (Not-a-Number). Number Properties Here is a list of each property and their description. Property Description MAX_VALUE The largest possible value a number in JavaScript can have 1.7976931348623157E+308 MIN_VALUE The smallest possible value a number in JavaScript can have 5E-324 NaN Equal to a value that is not a number. NEGATIVE_INFINITY A value that is less than MIN_VALUE. POSITIVE_INFINITY A value that is greater than MAX_VALUE prototype A static property of the Number object. Use the prototype property to assign new properties and methods to the Number object in the current document constructor Returns the function that created this object's instance. By default this is the Number object. 111 Javascript In the following sections, we will take a few examples to demonstrate the properties of Number. MAX_VALUE The Number.MAX_VALUE property belongs to the static Number object. It represents constants for the largest possible positive numbers that JavaScript can work with. The actual value of this constant is 1.7976931348623157 x 10308. Syntax The syntax to use MAX_VALUE is: var val = Number.MAX_VALUE; Example Try the following example to learn how to use MAX_VALUE. <html> <head> <script type="text/javascript"> <!-function showValue() { var val = Number.MAX_VALUE; document.write ("Value of Number.MAX_VALUE : " + val ); } //--> </script> </head> <body> <p>Click the following to see the result:</p> <form> <input type="button" value="Click Me" onclick="showValue();" /> 112 Javascript </form> </body> </html> Output Click the following to see the result: Click Me Value of Number.MAX_VALUE : 1.7976931348623157 x 10 308 MIN_VALUE The Number.MIN_VALUE property belongs to the static Number object. It represents constants for the smallest possible positive numbers that JavaScript can work with. The actual value of this constant is 5 x 10-324. Syntax The syntax to use MIN_VALUE is: var val = Number.MIN_VALUE; Example Try the following example. <html> <head> <script type="text/javascript"> <!-function showValue() { var val = Number.MIN_VALUE; alert("Value of Number.MIN_VALUE : " + val ); } //--> 113 Javascript </script> </head> <body> <p>Click the following to see the result:</p> <form> <input type="button" value="Click Me" onclick="showValue();" /> </form> </body> </html> Output Click the following to see the result: Click Me Value of Number.MIN_VALUE : 5e-324 NaN Unquoted literal constant NaN is a special value representing Not-a-Number. Since NaN always compares unequal to any number, including NaN, it is usually used to indicate an error condition for a function that should return a valid number. Note: Use the isNaN() global function to see if a value is an NaN value. Syntax The syntax to use NaN is: var val = Number.NaN; Example Try the following example to learn how to use NaN. <html> 114 Javascript <head> <script type="text/javascript"> <!-function showValue() { var dayOfMonth = 50; if (dayOfMonth < 1 || dayOfMonth > 31) { dayOfMonth = Number.NaN alert("Day of Month must be between 1 and 31.") } Document.write("Value of dayOfMonth : " + dayOfMonth ); } //--> </script> </head> <body> <p>Click the following to see the result:</p> <form> <input type="button" value="Click Me" onclick="showValue();" /> </form> </body> </html> Output Click the following to see the result: Click Me 115 Javascript Day of the Month must be between 1 and 31. NEGATIVE_INFINITY This is a special numeric value representing a value less than Number.MIN_VALUE. This value is represented as "-Infinity". It resembles an infinity in its mathematical behavior. For example, anything multiplied by NEGATIVE_INFINITY is NEGATIVE_INFINITY, and anything divided by NEGATIVE_INFINITY is zero. Because NEGATIVE_INFINITY is a constant, it is a read-only property of Number. Syntax The syntax to use NEGATIVE_INFINITY is as follows: var val = Number. NEGATIVE_INFINITY; Example Try the following example. <html> <head> <script type="text/javascript"> <!-function showValue() { var smallNumber = (-Number.MAX_VALUE) * 2 if (smallNumber == Number.NEGATIVE_INFINITY) { alert("Value of smallNumber : " + smallNumber ); } } //--> </script> </head> <body> <p>Click the following to see the result:</p> <form> 116 Javascript <input type="button" value="Click Me" onclick="showValue();" /> </form> </body> </html> Output Click the following to see the result: Click Me Value of val : -Infinity POSITIVE_INFINITY This is a special numeric value representing any value greater than Number.MAX_VALUE. This value is represented as "Infinity". It resembles an infinity in its mathematical behavior. For example, anything multiplied by POSITIVE_INFINITY is POSITIVE_INFINITY, and anything divided by POSITIVE_INFINITY is zero. As POSITIVE_INFINITY is a constant, it is a read-only property of Number. Syntax Use the following syntax to use POSITIVE_INFINITY. var val = Number. POSITIVE_INFINITY; Example Try the following example to learn how use POSITIVE_INFINITY. <html> <head> <script type="text/javascript"> <!-function showValue() { var bigNumber = Number.MAX_VALUE * 2 if (bigNumber == Number.POSITIVE_INFINITY) { 117 Javascript alert("Value of bigNumber : " + bigNumber ); } } //--> </script> </head> <body> <p>Click the following to see the result:</p> <form> <input type="button" value="Click Me" onclick="showValue();" /> </form> </body> </html> Output Click the following to see the result: Click Me Value of val : Infinity Prototype The prototype property allows you to add properties and methods to any object (Number, Boolean, String and Date etc.). Note: Prototype is a global property which is available with almost all the objects. Syntax Use the following syntax to use Prototype. object.prototype.name = value Example 118 Javascript Try the following example to use the prototype property to add a property to an object. <html> <head> <title>User-defined objects</title> <script type="text/javascript"> function book(title, author){ this.title = title; this.author = author; } </script> </head> <body> <script type="text/javascript"> var myBook = new book("Perl", "Mohtashim"); book.prototype.price = null; myBook.price = 100; document.write("Book title is : " + myBook.title + "<br>"); document.write("Book author is : " + myBook.author + "<br>"); document.write("Book price is : " + myBook.price + "<br>"); </script> </body> </html> Output Book title is : Perl Book author is : Mohtashim Book price is : 100 119 Javascript constructor It returns a reference to the Number function that created the instance's prototype. Syntax Its syntax is as follows: number.constructor() Return value Returns the function that created this object's instance. Example Try the following example. <html> <head> <title>JavaScript constructor() Method</title> </head> <body> <script type="text/javascript"> var num = new Number( 177.1234 ); document.write("num.constructor() is : " + num.constructor); </script> </body> </html> Output num.constructor() is : function Number() { [native code] } Number Methods The Number object contains only the default methods that are a part of every object's definition. Method Description toExponential() Forces a number to display in exponential notation, even if 120 Javascript the number is in the range in which JavaScript normally uses standard notation. toFixed() Formats a number with a specific number of digits to the right of the decimal. toLocaleString() Returns a string value version of the current number in a format that may vary according to a browser's local settings. toPrecision() Defines how many total digits (including digits to the left and right of the decimal) to display of a number. toString() Returns the string representation of the number's value. valueOf() Returns the number's value. In the following sections, we will have a few examples to explain the methods of Number. toExponential () This method returns a string representing the number object in exponential notation. Syntax Its syntax is as follows: number.toExponential( [fractionDigits] ) Parameter Details fractionDigits: An integer specifying the number of digits after the decimal point. Defaults to as many digits as necessary to specify the number. Return Value A string representing a Number object in exponential notation with one digit before the decimal point, rounded to fractionDigits digits after the decimal point. If the fractionDigits argument is omitted, the number of digits after the decimal point defaults to the number of digits necessary to represent the value uniquely. Example 121 Javascript Try the following example. <html> <head> <title>Javascript Method toExponential()</title> </head> <body> <script type="text/javascript"> var num=77.1234; var val = num.toExponential(); document.write("num.toExponential() is : " + val ); document.write("<br />"); val = num.toExponential(4); document.write("num.toExponential(4) is : " + val ); document.write("<br />"); val = num.toExponential(2); document.write("num.toExponential(2) is : " + val); document.write("<br />"); val = 77.1234.toExponential(); document.write("77.1234.toExponential()is : " + val ); document.write("<br />"); val = 77.1234.toExponential(); document.write("77 .toExponential() is : " + val); </script> </body> </html> Output num.toExponential() is : 7.71234e+1 num.toExponential(4) is : 7.7123e+1 122 Javascript num.toExponential(2) is : 7.71e+1 77.1234.toExponential()is : 7.71234e+1 77 .toExponential() is : 7.71234e+1 toFixed () This method formats a number with a specific number of digits to the right of the decimal. Syntax Its syntax is as follows: number.toFixed( [digits] ) Parameter Details digits: The number of digits to appear after the decimal point. Return Value A string representation of number that does not use exponential notation and has the exact number of digits after the decimal place. Example Try the following example. <html> <head> <title>JavaScript toFixed() Method</title> </head> <body> <script type="text/javascript"> var num=177.1234; document.write("num.toFixed() is : " + num.toFixed()); document.write("<br />"); document.write("num.toFixed(6) is : " + num.toFixed(6)); document.write("<br />"); document.write("num.toFixed(1) is : " + num.toFixed(1)); document.write("<br />"); document.write("(1.23e+20).toFixed(2) is:" + (1.23e+20).toFixed(2)); 123 Javascript document.write("<br />"); document.write("(1.23e-10).toFixed(2) is : " + (1.23e-10).toFixed(2)); </script> </body> </html> Output num.toFixed() is : 177 num.toFixed(6) is : 177.123400 num.toFixed(1) is : 177.1 (1.23e+20).toFixed(2) is:123000000000000000000.00 (1.23e-10).toFixed(2) is : 0.00 toLocaleString () This method converts a number object into a human representing the number using the locale of the environment. readable string Syntax Its syntax is as follows: number.toLocaleString() Return Value Returns a human readable string representing the number using the locale of the environment. Example Try the following example. <html> <head> <title>JavaScript toLocaleString() Method </title> </head> <body> <script type="text/javascript"> 124 Javascript var num = new Number(177.1234); document.write( num.toLocaleString()); </script> </body> </html> Output 177.123 toPrecision () This method returns a string representing the number object to the specified precision. Syntax Its syntax is as follows: number.toPrecision( [ precision ] ) Parameter Details precision: An integer specifying the number of significant digits. Return Value Returns a string representing a Number object in fixed-point or exponential notation rounded toprecision significant digits. Example Try the following example. <html> <head> <title>JavaScript toPrecision() Method </title> </head> <body> <script type="text/javascript"> var num = new Number(7.123456); 125 Javascript document.write("num.toPrecision() is " + num.toPrecision()); document.write("<br />"); document.write("num.toPrecision(4) is " + num.toPrecision(4)); document.write("<br />"); document.write("num.toPrecision(2) is " + num.toPrecision(2)); document.write("<br />"); document.write("num.toPrecision(1) is " + num.toPrecision(1)); </script> </body> </html> Output num.toPrecision() is 7.123456 num.toPrecision(4) is 7.123 num.toPrecision(2) is 7.1 num.toPrecision(1) is 7 toString () This method returns a string representing the specified object. The toString() method parses its first argument, and attempts to return a string representation in the specified radix (base). Syntax Its syntax is as follows: number.toString( [radix] ) Parameter Details radix: An integer between 2 and 36 specifying the base to use for representing numeric values. Return Value Returns a string representing the specified Number object. Example 126 Javascript Try the following example. <html> <head> <title>JavaScript toString() Method </title> </head> <body> <script type="text/javascript"> var num = new Number(15); document.write("num.toString() is " + num.toString()); document.write("<br />"); document.write("num.toString(2) is " + num.toString(2)); document.write("<br />"); document.write("num.toString(4) is " + num.toString(4)); document.write("<br />"); </script> </body> </html> Output num.toString() is 15 num.toString(2) is 1111 num.toString(4) is 33 valueOf () This method returns the primitive value of the specified number object. Syntax Its syntax is as follows: number.valueOf() Return Value 127 Javascript Returns the primitive value of the specified number object. Example Try the following example. <html> <head> <title>JavaScript valueOf() Method </title> </head> <body> <script type="text/javascript"> var num = new Number(15.11234); document.write("num.valueOf() is " + num.valueOf()); </script> </body> </html> Output num.valueOf() is 15.11234 128 22. BOOLEAN Javascript The Boolean object represents two values, either "true" or "false". If value parameter is omitted or is 0, -0, null, false, NaN, undefined, or the empty string (""), the object has an initial value of false. Syntax Use the following syntax to create a boolean object. var val = new Boolean(value); Boolean Properties Here is a list of the properties of Boolean object: Property Description constructor Returns a reference to the Boolean function that created the object. prototype The prototype property allows you to add properties and methods to an object. In the following sections, we will have a few examples to illustrate the properties of Boolean object. constructor () Javascript boolean constructor() method returns a reference to the Boolean function that created the instance's prototype. Syntax Use the following syntax to create a Boolean constructor() method. boolean.constructor() Return Value 129 Javascript Returns the function that created this object's instance. Example Try the following example. <html> <head> <title>JavaScript constructor() Method</title> </head> <body> <script type="text/javascript"> var bool = new Boolean( ); document.write("bool.constructor() is : " + bool.constructor); </script> </body> </html> Output bool.constructor() is : function Boolean() { [native code] } Prototype The prototype property allows you to add properties and methods to any object (Number, Boolean, String and Date, etc.). Note: Prototype is a global property which is available with almost all the objects. Syntax Use the following syntax to create a Boolean prototype. object.prototype.name = value Example 130 Javascript Try the following example; it shows how to use the prototype property to add a property to an object. <html> <head> <title>User-defined objects</title> <script type="text/javascript"> function book(title, author){ this.title = title; this.author = author; } </script> </head> <body> <script type="text/javascript"> var myBook = new book("Perl", "Mohtashim"); book.prototype.price = null; myBook.price = 100; document.write("Book title is : " + myBook.title + "<br>"); document.write("Book author is : " + myBook.author + "<br>"); document.write("Book price is : " + myBook.price + "<br>"); </script> </body> </html> Output Book title is : Perl Book author is : Mohtashim Book price is : 100 Boolean Methods Here is a list of the methods of Boolean object and their description. 131 Javascript Method Description toSource() Returns a string containing the source of the Boolean object; you can use this string to create an equivalent object. toString() Returns a string of either "true" or "false" depending upon the value of the object. valueOf() Returns the primitive value of the Boolean object. In the following sections, we will have a few examples to demonstrate the usage of the Boolean methods. toSource () Javascript boolean toSource() method returns a string representing the source code of the object. Note: This method is not compatible with all the browsers. Syntax Its syntax is as follows: boolean.toSource() Return Value Returns a string representing the source code of the object. Example Try the following example. <html> <head> <title>JavaScript toSource() Method</title> </head> <body> <script type="text/javascript"> function book(title, publisher, price) { 132 Javascript this.title = title; this.publisher = publisher; this.price = price; } var newBook = new book("Perl","Leo Inc",200); document.write("newBook.toSource() is : "+ newBook.toSource()); </script> </body> </html> Output ({title:"Perl", publisher:"Leo Inc", price:200}) toString () This method returns a string of either "true" or "false" depending upon the value of the object. Syntax Its syntax is as follows: boolean.toString() Return Value Returns a string representing the specified Boolean object. Example Try the following example. <html> <head> <title>JavaScript toString() Method</title> </head> <body> <script type="text/javascript"> var flag = new Boolean(false); document.write( "flag.toString is : " + flag.toString() ); 133 Javascript </script> </body> </html> Output flag.toString is : false valueOf () Javascript boolean valueOf() method returns the primitive value of the specified boolean object. Syntax Its syntax is as follows: boolean.valueOf() Return Value Returns the primitive value of the specified boolean object. Example Try the following example. <html> <head> <title>JavaScript toString() Method</title> </head> <body> <script type="text/javascript"> var flag = new Boolean(false); document.write( "flag.valueOf is : " + flag.valueOf() ); </script> </body> </html> Output flag.valueOf is : false 134 Javascript 135 23. STRING Javascript The String object lets you work with a series of characters; it wraps Javascript's string primitive data type with a number of helper methods. As JavaScript automatically converts between string primitives and String objects, you can call any of the helper methods of the String object on a string primitive. Syntax Use the following syntax to create a String object: var val = new String(string); The string parameter is a series of characters that has been properly encoded. String Properties Here is a list of the properties of String object and their description. Property Description constructor Returns a reference to the String function that created the object. length Returns the length of the string. prototype The prototype property allows you to add properties and methods to an object. In the following sections, we will have a few examples to demonstrate the usage of String properties. constructor A constructor returns a reference to the string function that created the instance's prototype. 136 Javascript Syntax Its syntax is as follows: string.constructor Return Value Returns the function that created this object's instance. Example Try the following example. <html> <head> <title>JavaScript String constructor property</title> </head> <body> <script type="text/javascript"> var str = new String( "This is string" ); document.write("str.constructor is:" + str.constructor); </script> </body> </html> Output str.constructor is:function String() { [native code] } Length This property returns the number of characters in a string. Syntax Use the following syntax to find the length of a string: string.length Return Value Returns the number of characters in the string. Example 137 Javascript Try the following example. <html> <head> <title>JavaScript String length Property</title> </head> <body> <script type="text/javascript"> var str = new String( "This is string" ); document.write("str.length is:" + str.length); </script> </body> </html> Output str.length is:14 Prototype The prototype property allows you to add properties and methods to any object (Number, Boolean, String, Date, etc.). Note: Prototype is a global property which is available with almost all the objects. Syntax Its syntax is as follows: object.prototype.name = value Example Try the following example. <html> <head> <title>User-defined objects</title> <script type="text/javascript"> 138 Javascript function book(title, author){ this.title = title; this.author = author; } </script> </head> <body> <script type="text/javascript"> var myBook = new book("Perl", "Mohtashim"); book.prototype.price = null; myBook.price = 100; document.write("Book title is : " + myBook.title + "<br>"); document.write("Book author is : " + myBook.author + "<br>"); document.write("Book price is : " + myBook.price + "<br>"); </script> </body> </html> Output Book title is : Perl Book author is : Mohtashim Book price is : 100 String Methods Here is a list of the methods available in String object along with their description. Method Description charAt() Returns the character at the specified index. charCodeAt() Returns a number indicating the Unicode value of the character at the given index. 139 Javascript concat() Combines the text of two strings and returns a new string. indexOf() Returns the index within the calling String object of the first occurrence of the specified value, or -1 if not found. lastIndexOf() Returns the index within the calling String object of the last occurrence of the specified value, or -1 if not found. localeCompare() Returns a number indicating whether a reference string comes before or after or is the same as the given string in sorted order. match() Used to match a regular expression against a string. replace() Used to find a match between a regular expression and a string, and to replace the matched substring with a new substring. search() Executes the search for a match between a regular expression and a specified string. slice() Extracts a section of a string and returns a new string. split() Splits a String object into an array of strings by separating the string into substrings. substr() Returns the characters in a string beginning at the specified location through the specified number of characters. substring() Returns the characters in a string between two indexes into the string. toLocaleLowerCase() The characters within a string are converted to lower case while respecting the current locale. toLocaleUpperCase() The characters within a string are converted to upper case while respecting the current locale. toLowerCase() Returns the calling string value converted to lower case. toString() Returns a string representing the specified object. 140 Javascript toUpperCase() Returns the calling string value converted to uppercase. valueOf() Returns the primitive value of the specified object. In the following sections, we will have a few examples to demonstrate the usage of String methods. charAt() charAt() is a method that returns the character from the specified index. Characters in a string are indexed from left to right. The index of the first character is 0, and the index of the last character in a string, called stringName, is stringName.length – 1. Syntax Use the following syntax to find the character at a particular index. string.charAt(index) Argument Details index: An integer between 0 and 1 less than the length of the string. Return Value Returns the character from the specified index. Example Try the following example. <html> <head> <title>JavaScript String charAt() Method</title> </head> <body> <script type="text/javascript"> var str = new String( "This is string" ); document.writeln("str.charAt(0) is:" + str.charAt(0)); document.writeln("<br />str.charAt(1) is:" + str.charAt(1)); document.writeln("<br />str.charAt(2) is:" + str.charAt(2)); 141 Javascript document.writeln("<br />str.charAt(3) is:" + str.charAt(3)); document.writeln("<br />str.charAt(4) is:" + str.charAt(4)); document.writeln("<br />str.charAt(5) is:" + str.charAt(5)); </script> </body> </html> Output str.charAt(0) str.charAt(1) str.charAt(2) str.charAt(3) str.charAt(4) str.charAt(5) is:T is:h is:i is:s is: is:i charCodeAt () This method returns a number indicating the Unicode value of the character at the given index. Unicode code points range from 0 to 1,114,111. The first 128 Unicode code points are a direct match of the ASCII character encoding. charCodeAt() always returns a value that is less than 65,536. Syntax Use the following syntax to find the character code at a particular index. string.charCodeAt(index) Argument Details index: An integer between 0 and 1 less than the length of the string; if unspecified, defaults to 0. Return Value Returns a number indicating the Unicode value of the character at the given index. It returns NaN if the given index is not between 0 and 1 less than the length of the string. Example 142 Javascript Try the following example. <html> <head> <title>JavaScript String charCodeAt() Method</title> </head> <body> <script type="text/javascript"> var str = new String( "This is string" ); document.write("str.charCodeAt(0) is:" + str.charCodeAt(0)); document.write("<br />str.charCodeAt(1) is:" + str.charCodeAt(1)); document.write("<br />str.charCodeAt(2) is:" + str.charCodeAt(2)); document.write("<br />str.charCodeAt(3) is:" + str.charCodeAt(3)); document.write("<br />str.charCodeAt(4) is:" + str.charCodeAt(4)); document.write("<br />str.charCodeAt(5) is:" + str.charCodeAt(5)); </script> </body> </html> Output str.charCodeAt(0) str.charCodeAt(1) str.charCodeAt(2) str.charCodeAt(3) str.charCodeAt(4) str.charCodeAt(5) is:84 is:104 is:105 is:115 is:32 is:105 contact () This method adds two or more strings and returns a new single string. Syntax Its syntax is as follows: string.concat(string2, string3[, ..., stringN]); 143 Javascript Argument Details string2...stringN: These are the strings to be concatenated. Return Value Returns a single concatenated string. Example Try the following example. <html> <head> <title>JavaScript String concat() Method</title> </head> <body> <script type="text/javascript"> var str1 = new String( "This is string one" ); var str2 = new String( "This is string two" ); var str3 = str1.concat( str2 ); document.write("Concatenated String :" + str3); </script> </body> </html> Output Concatenated String :This is string one This is string two indexOf () This method returns the index within the calling String object of the first occurrence of the specified value, starting the search at fromIndex or -1 if the value is not found. Syntax Use the following syntax to use the indexOf() method. string.indexOf(searchValue[, fromIndex]) 144 Javascript Argument Details   searchValue: A string representing the value to search for. fromIndex: The location within the calling string to start the search from. It can be any integer between 0 and the length of the string. The default value is 0. Return Value Returns the index of the found occurrence, otherwise -1 if not found. Example Try the following example. <html> <head> <title>JavaScript String indexOf() Method</title> </head> <body> <script type="text/javascript"> var str1 = new String( "This is string one" ); var index = str1.indexOf( "string" ); document.write("indexOf found String :" + index ); document.write("<br />"); var index = str1.indexOf( "one" ); document.write("indexOf found String :" + index ); </script> </body> </html> Output indexOf found String :8 indexOf found String :15 145 Javascript lastIndexOf () This method returns the index within the calling String object of the last occurrence of the specified value, starting the search at fromIndex or -1 if the value is not found. Syntax Its syntax is as follows: string.lastIndexOf(searchValue[, fromIndex]) Argument Details   searchValue : A string representing the value to search for. fromIndex : The location within the calling string to start the search from. It can be any integer between 0 and the length of the string. The default value is 0. Return Value Returns the index of the last found occurrence, otherwise -1 if not found. Example Try the following example. <html> <head> <title>JavaScript String lastIndexOf() Method</title> </head> <body> <script type="text/javascript"> var str1 = new String( "This is string one and again string" ); var index = str1.lastIndexOf( "string" ); document.write("lastIndexOf found String :" + index ); document.write("<br />"); var index = str1.lastIndexOf( "one" ); document.write("lastIndexOf found String :" + index ); </script> 146 Javascript </body> </html> Output lastIndexOf found String :29 lastIndexOf found String :15 localeCompare () This method returns a number indicating whether a reference string comes before or after or is the same as the given string in sorted order. Syntax The syntax of localeCompare() method is: string.localeCompare( param ) Argument Details param : A string to be compared with string object. Return Value    0 : If the string matches 100%. 1 : no match, and the parameter value comes before the string object's value in the locale sort order -1 : no match, and the parameter value comes after the string object's value in the local sort order Example Try the following example. <html> <head> <title>JavaScript String localeCompare() Method</title> </head> <body> <script type="text/javascript"> var str1 = new String( "This is beautiful string" ); 147 Javascript var index = str1.localeCompare( "XYZ" ); document.write("localeCompare first :" + index ); document.write("<br />" ); var index = str1.localeCompare( "AbCD ?" ); document.write("localeCompare second :" + index ); </script> </body> </html> Output localeCompare first :-1 localeCompare second :1 match () This method is used to retrieve the matches when matching a string against a regular expression. Syntax Use the following syntax to use the match() method. string.match ( param ) Argument Details param : A regular expression object. Return Value   If the regular expression does not include the g flag, it returns the same result as regexp.exec(string). If the regular expression includes the g flag, the method returns an Array containing all the matches. Example Try the following example. 148 Javascript <html> <head> <title>JavaScript String match() Method</title> </head> <body> <script type="text/javascript"> var str = "For more information, see Chapter 3.4.5.1"; var re = /(chapter \d+(\.\d)*)/i; var found = str.match( re ); document.write(found ); </script> </body> </html> Output Chapter 3.4.5.1,Chapter 3.4.5.1,.1 replace () This method finds a match between a regular expression and a string, and replaces the matched substring with a new substring. The replacement string can include the following special replacement patterns: Pattern Inserts $$ Inserts a "$". $& Inserts the matched substring. $` Inserts the portion of the string that precedes the matched substring. $' Inserts the portion of the string that follows the matched 149 Javascript substring. $n or $nn Where n or nn are decimal digits, inserts the nth parenthesized submatch string, provided the first argument was a RegExp object. Syntax The syntax to use the replace() method is as follows: string.replace(regexp/substr, newSubStr/function[, flags]); Argument Details      regexp : A RegExp object. The match is replaced by the return value of parameter #2. substr : A String that is to be replaced by newSubStr. newSubStr : The String that replaces the substring received from parameter #1. function : A function to be invoked to create the new substring. flags : A String containing any combination of the RegExp flags: g global match, i - ignore case, m - match over multiple lines. This parameter is only used if the first parameter is a string. Return Value It simply returns a new changed string. Example Try the following example. <html> <head> <title>JavaScript String replace() Method</title> </head> <body> <script type="text/javascript"> var re = /apples/gi; 150 Javascript var str = "Apples are round, and apples are juicy."; var newstr = str.replace(re, "oranges"); document.write(newstr ); </script> </body> </html> Output oranges are round, and oranges are juicy. Example Try the following example; it shows how to switch words in a string. <html> <head> <title>JavaScript String replace() Method</title> </head> <body> <script type="text/javascript"> var re = /(\w+)\s(\w+)/; var str = "zara ali"; var newstr = str.replace(re, "$2, $1"); document.write(newstr); </script> </body> </html> Output ali, zara 151 Javascript Search () This method executes the search for a match between a regular expression and this String object. Syntax Its syntax is as follows: string.search(regexp); Argument Details regexp : A regular expression object. If a non-RegExp object obj is passed, it is implicitly converted to a RegExp by using new RegExp(obj). Return Value If successful, the search returns the index of the regular expression inside the string. Otherwise, it returns -1. Example Try the following example. <html> <head> <title>JavaScript String search() Method</title> </head> <body> <script type="text/javascript"> var re = /apples/gi; var str = "Apples are round, and apples are juicy."; if ( str.search(re) == -1 ){ document.write("Does not contain Apples" ); }else{ document.write("Contains Apples" ); } </script> 152 Javascript </body> </html> Output Contains Apples slice () This method extracts a section of a string and returns a new string. Syntax The syntax for slice() method is: string.slice( beginslice [, endSlice] ); Argument Details   beginSlice : The zero-based index at which to begin extraction. endSlice : The zero-based index at which to end extraction. If omitted, slice extracts to the end of the string. Return Value If successful, slice returns the index of the regular expression inside the string. Otherwise, it returns -1. Example Try the following example. <html> <head> <title>JavaScript String slice() Method</title> </head> <body> <script type="text/javascript"> var str = "Apples are round, and apples are juicy."; var sliced = str.slice(3, -2); 153 Javascript document.write( sliced ); </script> </body> </html> Output les are round, and apples are juic split () This method splits a String object into an array of strings by separating the string into substrings. Syntax Its syntax is as follows: string.split([separator][, limit]); Argument Details   separator : Specifies the character to use for separating the string. If separator is omitted, the array returned contains one element consisting of the entire string. limit : Integer specifying a limit on the number of splits to be found. Return Value The split method returns the new array. Also, when the string is empty, split returns an array containing one empty string, rather than an empty array. Example Try the following example. <html> <head> 154 Javascript <title>JavaScript String split() Method</title> </head> <body> <script type="text/javascript"> var str = "Apples are round, and apples are juicy."; var splitted = str.split(" ", 3); document.write( splitted ); </script> </body> </html> Output Apples,are,round, substr () This method returns the characters in a string beginning at the specified location through the specified number of characters. Syntax The syntax to use substr() is as follows: string.substr(start[, length]); Argument Details   start : Location at which to start extracting characters (an integer between 0 and one less than the length of the string). length : The number of characters to extract. Note: If start is negative, substr uses it as a character index from the end of the string. Return Value The substr() method returns the new sub-string based on given parameters. Example 155 Javascript Try the following example. <html> <head> <title>JavaScript String substr() Method</title> </head> <body> <script type="text/javascript"> var str = "Apples are round, and apples are juicy."; document.write("(1,2): " + str.substr(1,2)); document.write("<br />(-2,2): " + str.substr(-2,2)); document.write("<br />(1): " + str.substr(1)); document.write("<br />(-20, 2): " + str.substr(-20,2)); document.write("<br />(20, 2): " + str.substr(20,2)); </script> </body> </html> Output (1,2): pp (-2,2): y. (1): pples are round, and apples are juicy. (-20, 2): nd (20, 2): d substring () This method returns a subset of a String object. Syntax The syntax to use substr() is as follows: string.substring(indexA, [indexB]) Argument Details 156 Javascript   indexA : An integer between 0 and one less than the length of the string. indexB : (optional) An integer between 0 and the length of the string. Return Value The substring method returns the new sub-string based on given parameters. Example Try the following example. <html> <head> <title>JavaScript String substring() Method</title> </head> <body> <script type="text/javascript"> var str = "Apples are round, and apples are juicy."; document.write("(1,2): " + str.substring(1,2)); document.write("<br />(0,10): " + str.substring(0, 10)); document.write("<br />(5): " + str.substring(5)); </script> </body> </html> Output (1,2): p (0,10): Apples are (5): s are round, and apples are juicy. toLocaleLowerCase() This method is used to convert the characters within a string to lowercase while respecting the current locale. For most languages, it returns the same output as toLowerCase. Syntax Its syntax is as follows: string.toLocaleLowerCase( ) 157 Javascript Return Value Returns a string in lowercase with the current locale. Example Try the following example. <html> <head> <title>JavaScript String toLocaleLowerCase() Method</title> </head> <body> <script type="text/javascript"> var str = "Apples are round, and Apples are Juicy."; document.write(str.toLocaleLowerCase( )); </script> </body> </html> Output apples are round, and apples are juicy. toLocaleUppereCase () This method is used to convert the characters within a string to uppercase while respecting the current locale. For most languages, it returns the same output as toUpperCase. Syntax Its syntax is as follows: string.toLocaleUpperCase( ) Return Value Returns a string in uppercase with the current locale. 158 Javascript Example Try the following example. <html> <head> <title>JavaScript String toLocaleUpperCase() Method</title> </head> <body> <script type="text/javascript"> var str = "Apples are round, and Apples are Juicy."; document.write(str.toLocaleUpperCase( )); </script> </body> </html> Output APPLES ARE ROUND, AND APPLES ARE JUICY. toLowerCase () This method returns the calling string value converted to lowercase. Syntax Its syntax is as follows: string.toLowerCase( ) Return Value Returns the calling string value converted to lowercase. Example Try the following example. <html> 159 Javascript <head> <title>JavaScript String toLowerCase() Method</title> </head> <body> <script type="text/javascript"> var str = "Apples are round, and Apples are Juicy."; document.write(str.toLowerCase( )); </script> </body> </html> Output apples are round, and apples are juicy. toString () This method returns a string representing the specified object. Syntax Its syntax is as follows: string.toString( ) Return Value Returns a string representing the specified object. Example Try the following example. <html> <head> <title>JavaScript String toString() Method</title> </head> 160 Javascript <body> <script type="text/javascript"> var str = "Apples are round, and Apples are Juicy."; document.write(str.toString( )); </script> </body> </html> Output Apples are round, and Apples are Juicy. toUpperCase () This method returns the calling string value converted to uppercase. Syntax Its syntax is as follows: string.toUpperCase( ) Return Value Returns a string representing the specified object. Example Try the following example. <html> <head> <title>JavaScript String toUpperCase() Method</title> </head> <body> 161 Javascript <script type="text/javascript"> var str = "Apples are round, and Apples are Juicy."; document.write(str.toUpperCase( )); </script> </body> </html> Output APPLES ARE ROUND, AND APPLES ARE JUICY. valueOf () This method returns the primitive value of a String object. Syntax Its syntax is as follows: string.valueOf( ) Return Value Returns the primitive value of a String object. Example Try the following example. <html> <head> <title>JavaScript String valueOf() Method</title> </head> <body> <script type="text/javascript"> var str = new String("Hello world"); document.write(str.valueOf( )); </script> </body> </html> 162 Javascript Output Hello world String HTML Wrappers Here is a list of the methods that return a copy of the string wrapped inside an appropriate HTML tag. Method Description anchor() Creates an HTML anchor that is used as a hypertext target. big() Creates a string to be displayed in a big font as if it were in a <big> tag. blink() Creates a string to blink as if it were in a <blink> tag. bold() Creates a string to be displayed as bold as if it were in a <b> tag. fixed() Causes a string to be displayed in fixed-pitch font as if it were in a <tt> tag fontcolor() Causes a string to be displayed in the specified color as if it were in a <font color="color"> tag. fontsize() Causes a string to be displayed in the specified font size as if it were in a <font size="size"> tag. italics() Causes a string to be italic, as if it were in an <i> tag. link() Creates an HTML hypertext link that requests another URL. small() Causes a string to be displayed in a small font, as if it were in a <small> tag. strike() Causes a string to be displayed as struck-out text, as if it were in a <strike> tag. sub() Causes a string to be displayed as a subscript, as if it 163 Javascript were in a <sub> tag sup() Causes a string to be displayed as a superscript, as if it were in a <sup> tag In the following sections, we will have a few examples to demonstrate the usage of string HTML wrappers. anchor() This method creates an HTML anchor that is used as a hypertext target. Syntax Its syntax is as follows: string.anchor( anchorname ) Attribute details anchorname: Defines a name for the anchor. Return Value Returns the string having the anchor tag. Example Try the following example. <html> <head> <title>JavaScript String anchor() Method</title> </head> <body> <script type="text/javascript"> var str = new String("Hello world"); alert (str.anchor( "myanchor" )); </script> </body> </html> 164 Javascript Output <a name="myanchor">Hello world</a> big() This method causes a string to be displayed in a big font as if it were in a BIG tag. Syntax The syntax to use big() is as follows: string.big() Return Value Returns the string having <big> tag. Example Try the following example. <html> <head> <title>JavaScript String big() Method</title> </head> <body> <script type="text/javascript"> var str = new String("Hello world"); alert(str.big()); </script> </body> </html> Output <big>Hello world</big> 165 Javascript blink () This method causes a string to blink as if it were in a BLINK tag. Syntax The syntax for blink() method is as follows: string.blink( ) Return Value Returns the string having <blink> tag. Example Try the following example. <html> <head> <title>JavaScript String blink() Method</title> </head> <body> <script type="text/javascript"> var str = new String("Hello world"); alert(str.blink()); </script> </body> </html> Output <blink>Hello world</blink> bold () This method causes a string to be displayed as bold as if it were in a <b> tag. Syntax The syntax for bold() method is as follows: 166 Javascript string.bold( ) Return Value Returns the string having <bold> tag. Example Try the following example. <html> <head> <title>JavaScript String bold() Method</title> </head> <body> <script type="text/javascript"> var str = new String("Hello world"); alert(str.bold()); </script> </body> </html> Output <b>Hello world</b> fixed () This method causes a string to be displayed in fixed-pitch font as if it were in a <tt> tag. Syntax Its syntax is as follows: string.fixed( ) Return Value Returns the string having <tt> tag. Example 167 Javascript Try the following example. <html> <head> <title>JavaScript String fixed() Method</title> </head> <body> <script type="text/javascript"> var str = new String("Hello world"); alert(str.fixed()); </script> </body> </html> Output <tt>Hello world</tt> fontColor () This method causes a string to be displayed in the specified color as if it were in a <font color="color"> tag. Syntax Its syntax is as follows: string.fontColor( color) Attribute Details color: A string expressing the color as a hexadecimal RGB triplet or as a string literal. Return Value Returns the string with <font color="color"> tag. Example Try the following example. <html> 168 Javascript <head> <title>JavaScript String fontcolor() Method</title> </head> <body> <script type="text/javascript"> var str = new String("Hello world"); alert(str.fontcolor( "red" )); </script> </body> </html> Output <font color="red">Hello world</font> fontsize () This method causes a string to be displayed in the specified size as if it were in a <font size="size"> tag. Syntax Its syntax is as follows: string.fontsize( size ) Attribute Details size: An integer between 1 and 7, a string representing a signed integer between 1 and 7. Return Value Returns the string with <font size="size"> tag. Example Try the following example. 169 Javascript <html> <head> <title>JavaScript String fontsize() Method</title> </head> <body> <script type="text/javascript"> var str = new String("Hello world"); alert(str.fontsize( 3 )); </script> </body> </html> Output <font size="3">Hello world</font> italics () This method causes a string to be italic, as if it were in an <i> tag. Syntax Its syntax is as follows: string.italics ( ) Return Value Returns the string with <i> tag. Example Try the following example. <html> 170 Javascript <head> <title>JavaScript String italics() Method</title> </head> <body> <script type="text/javascript"> var str = new String("Hello world"); alert(str.italics( )); </script> </body> </html> Output <i>Hello world</i> link () This method creates an HTML hypertext link that requests another URL. Syntax The syntax for link() method is as follows: string.link ( hrefname ) Attribute Details hrefname: Any string that specifies the HREF of the A tag; it should be a valid URL. Return Value Returns the string with <a> tag. Example Try the following example. <html> 171 Javascript <head> <title>JavaScript String link() Method</title> </head> <body> <script type="text/javascript"> var str = new String("Hello world"); var URL = "http://www.tutorialspoint.com"; alert(str.link( URL )); </script> </body> </html> Output <a href = http://www.tutorialspoint.com >Hello world</a> small () This method causes a string to be displayed in a small font, as if it were in a <small> tag. Syntax Its syntax is as follows: string.small ( ) Return Value Returns the string with <small> tag. Example Try the following example. <html> 172 Javascript <head> <title>JavaScript String small() Method</title> </head> <body> <script type="text/javascript"> var str = new String("Hello world"); alert(str.small()); </script> </body> </html> Output <small>Hello world</small> strike () This method causes a string to be displayed as struck-out text, as if it were in a <strike> tag. Syntax Its syntax is as follows: string.strike ( ) Return Value Returns the string with <strike> tag. Example Try the following example. <html> 173 Javascript <head> <title>JavaScript String strike() Method</title> </head> <body> <script type="text/javascript"> var str = new String("Hello world"); alert(str.strike()); </script> </body> </html> Output <strike>Hello world</strike> sub() This method causes a string to be displayed as a subscript, as if it were in a <sub> tag. Syntax Its syntax is as follows: string.sub ( ) Return Value Returns the string with <sub> tag. Example Try the following example. 174 Javascript <html> <head> <title>JavaScript String sub() Method</title> </head> <body> <script type="text/javascript"> var str = new String("Hello world"); alert(str.sub()); </script> </body> </html> Output _{Hello world} sup () This method causes a string to be displayed as a superscript, as if it were in a <sup> tag. Syntax Its syntax is as follows: string.sup() Return Value Returns the string with <sup> tag. Example Try the following example. 175 Javascript <html> <head> <title>JavaScript String sup() Method</title> </head> <body> <script type="text/javascript"> var str = new String("Hello world"); alert(str.sup()); </script> </body> </html> Output ^{Hello world} 176 24. ARRAYS Javascript The Array object lets you store multiple values in a single variable. It stores a fixed-size sequential collection of elements of the same type. An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type. Syntax Use the following syntax to create an Array Object. var fruits = new Array( "apple", "orange", "mango" ); The Array parameter is a list of strings or integers. When you specify a single numeric parameter with the Array constructor, you specify the initial length of the array. The maximum length allowed for an array is 4,294,967,295. You can create array by simply assigning values as follows: var fruits = [ "apple", "orange", "mango" ]; You will use ordinal numbers to access and to set values inside an array as follows. fruits[0] is the first element fruits[1] is the second element fruits[2] is the third element Array Properties Here is a list of the properties of the Array object along with their description. Property Description constructor Returns a reference to the array function that created the object. index The property represents the zero-based index of the match in the string 177 Javascript input This property is only present in arrays created by regular expression matches. length Reflects the number of elements in an array. prototype The prototype property allows you to add properties and methods to an object. In the following sections, we will have a few examples to illustrate the usage of Array properties. constructor Javascript array constructor property returns a reference to the array function that created the instance's prototype. Syntax Its syntax is as follows: array.constructor Return Value Returns the function that created this object's instance. Example Try the following example. <html> <head> <title>JavaScript Array constructor Property</title> </head> <body> <script type="text/javascript"> var arr = new Array( 10, 20, 30 ); document.write("arr.constructor is:" + arr.constructor); </script> </body> </html> 178 Javascript Output arr.constructor is:function Array() { [native code] } length Javascript array length property returns an unsigned, 32-bit integer that specifies the number of elements in an array. Syntax Its syntax is as follows: array.length Return Value Returns the length of an array. Example Try the following example. <html> <head> <title>JavaScript Array length Property</title> </head> <body> <script type="text/javascript"> var arr = new Array( 10, 20, 30 ); document.write("arr.length is:" + arr.length); </script> </body> </html> Output arr.length is:3 179 Javascript Prototype The prototype property allows you to add properties and methods to any object (Number, Boolean, String, Date, etc.). Note: Prototype is a global property which is available with almost all the objects. Syntax Its syntax is as follows: object.prototype.name = value Example Try the following example. <html> <head> <title>User-defined objects</title> <script type="text/javascript"> function book(title, author){ this.title = title; this.author = author; } </script> </head> <body> <script type="text/javascript"> var myBook = new book("Perl", "Mohtashim"); book.prototype.price = null; myBook.price = 100; document.write("Book title is : " + myBook.title + "<br>"); document.write("Book author is : " + myBook.author + "<br>"); document.write("Book price is : " + myBook.price + "<br>"); </script> 180 Javascript </body> </html> Output Book title is : Perl Book author is : Mohtashim Book price is : 100 Array Methods Here is a list of the methods of the Array object along with their description. Method Description concat() Returns a new array comprised of this array joined with other array(s) and/or value(s). every() Returns true if every element in this array satisfies the provided testing function. filter() Creates a new array with all of the elements of this array for which the provided filtering function returns true. forEach() Calls a function for each element in the array. indexOf() Returns the first (least) index of an element within the array equal to the specified value, or 1 if none is found. join() Joins all elements of an array into a string. lastIndexOf() Returns the last (greatest) index of an element within the array equal to the specified value, or 1 if none is found. map() Creates a new array with the results of calling a provided function on every element in this array. pop() Removes the last element from an array and returns that element. 181 Javascript push() Adds one or more elements to the end of an array and returns the new length of the array. reduce() Apply a function simultaneously against two values of the array (from left-to-right) as to reduce it to a single value. reduceRight() Apply a function simultaneously against two values of the array (from right-to-left) as to reduce it to a single value. reverse() Reverses the order of the elements of an array -the first becomes the last, and the last becomes the first. shift() Removes the first element from an array and returns that element. slice() Extracts a section of an array and returns a new array. some() Returns true if at least one element in this array satisfies the provided testing function. toSource() Represents the source code of an object sort() Sorts the elements of an array. splice() Adds and/or removes elements from an array. toString() Returns a string representing the array and its elements. unshift() Adds one or more elements to the front of an array and returns the new length of the array. In the following sections, we will have a few examples to demonstrate the usage of Array methods. 182 Javascript concat () Javascript array concat() method returns a new array comprised of this array joined with two or more arrays. Syntax The syntax of concat() method is as follows: array.concat(value1, value2, ..., valueN); Parameter Details valueN : Arrays and/or values to concatenate to the resulting array. Return Value Returns the length of the array. Example Try the following example. <html> <head> <title>JavaScript Array concat Method</title> </head> <body> <script type="text/javascript"> var alpha = ["a", "b", "c"]; var numeric = [1, 2, 3]; var alphaNumeric = alpha.concat(numeric); document.write("alphaNumeric : " + alphaNumeric ); </script> </body> </html> Output alphaNumeric : a,b,c,1,2,3 183 Javascript every () Javascript array every method tests whether all the elements in an array passes the test implemented by the provided function. Syntax Its syntax is as follows: array.every(callback[, thisObject]); Parameter Details   callback : Function to test for each element. thisObject : Object to use as this when executing callback. Return Value Returns true if every element in this array satisfies the provided testing function. Compatibility This method is a JavaScript extension to the ECMA-262 standard; as such it may not be present in other implementations of the standard. To make it work, you need to add the following code at the top of your script. if (!Array.prototype.every) { Array.prototype.every = function(fun /*, thisp*/) { var len = this.length; if (typeof fun != "function") throw new TypeError(); var thisp = arguments[1]; for (var i = 0; i < len; i++) { if (i in this && !fun.call(thisp, this[i], i, this)) return false; } 184 Javascript return true; }; } Example Try the following example. <html> <head> <title>JavaScript Array every Method</title> </head> <body> <script type="text/javascript"> if (!Array.prototype.every) { Array.prototype.every = function(fun /*, thisp*/) { var len = this.length; if (typeof fun != "function") throw new TypeError(); var thisp = arguments[1]; for (var i = 0; i < len; i++) { if (i in this && !fun.call(thisp, this[i], i, this)) return false; } return true; }; } function isBigEnough(element, index, array) { return (element >= 10); 185 Javascript } var passed = [12, 5, 8, 130, 44].every(isBigEnough); document.write("First Test Value : " + passed ); passed = [12, 54, 18, 130, 44].every(isBigEnough); document.write("Second Test Value : " + passed ); </script> </body> </html> Output First Test Value : falseSecond Test Value : true filter () Javascript array filter() method creates a new array with all elements that pass the test implemented by the provided function. Syntax Its syntax is as follows: array.filter (callback[, thisObject]); Parameter Details   callback : Function to test for each element of an array. thisObject : Object to use as this when executing callback. Return Value Returns created array. Compatibility This method is a JavaScript extension to the ECMA-262 standard; as such it may not be present in other implementations of the standard. To make it work, you need to add the following code at the top of your script. if (!Array.prototype.filter) 186 Javascript { Array.prototype.filter = function(fun /*, thisp*/) { var len = this.length; if (typeof fun != "function") throw new TypeError(); var res = new Array(); var thisp = arguments[1]; for (var i = 0; i < len; i++) { if (i in this) { var val = this[i]; // in case fun mutates this if (fun.call(thisp, val, i, this)) res.push(val); } } return res; }; } Example Try the following example. <html> <head> <title>JavaScript Array filter Method</title> </head> <body> <script type="text/javascript"> if (!Array.prototype.filter) { 187 Javascript Array.prototype.filter = function(fun /*, thisp*/) { var len = this.length; if (typeof fun != "function") throw new TypeError(); var res = new Array(); var thisp = arguments[1]; for (var i = 0; i < len; i++) { if (i in this) { var val = this[i]; // in case fun mutates this if (fun.call(thisp, val, i, this)) res.push(val); } } return res; }; } function isBigEnough(element, index, array) { return (element >= 10); } var filtered = [12, 5, 8, 130, 44].filter(isBigEnough); document.write("Filtered Value : " + filtered ); </script> </body> </html> Output 188 Javascript Filtered Value : 12,130,44 forEach () Javascript array forEach() method calls a function for each element in the array. Syntax Its syntax is as follows: array.forEach(callback[, thisObject]); Parameter Details   callback : Function to test for each element of an array. thisObject : Object to use as this when executing callback. Return Value Returns the created array. Compatibility This method is a JavaScript extension to the ECMA-262 standard; as such it may not be present in other implementations of the standard. To make it work, you need to add following code at the top of your script. if (!Array.prototype.forEach) { Array.prototype.forEach = function(fun /*, thisp*/) { var len = this.length; if (typeof fun != "function") throw new TypeError(); var thisp = arguments[1]; for (var i = 0; i < len; i++) { if (i in this) fun.call(thisp, this[i], i, this); } 189 Javascript }; } Example Try the following example. <html> <head> <title>JavaScript Array forEach Method</title> </head> <body> <script type="text/javascript"> if (!Array.prototype.forEach) { Array.prototype.forEach = function(fun /*, thisp*/) { var len = this.length; if (typeof fun != "function") throw new TypeError(); var thisp = arguments[1]; for (var i = 0; i < len; i++) { if (i in this) fun.call(thisp, this[i], i, this); } }; } function printBr(element, index, array) { document.write("<br />[" + index + "] is " + element ); } [12, 5, 8, 130, 44].forEach(printBr); 190 Javascript </script> </body> </html> Output [0] [1] [2] [3] [4] is is is is is 12 5 8 130 44 indexOf () Javascript array indexOf() method returns the first index at which a given element can be found in the array, or -1 if it is not present. Syntax Its syntax is as follows: array.indexOf(searchElement[, fromIndex]); Parameter Details   searchElement : Element to locate in the array. fromIndex : The index at which to begin the search. Defaults to 0, i.e. the whole array will be searched. If the index is greater than or equal to the length of the array, -1 is returned. Return Value Returns the index of the found element. Compatibility This method is a JavaScript extension to the ECMA-262 standard; as such it may not be present in other implementations of the standard. To make it work, you need to add the following code at the top of your script. if (!Array.prototype.indexOf) { Array.prototype.indexOf = function(elt /*, from*/) { 191 Javascript var len = this.length; var from = Number(arguments[1]) || 0; from = (from < 0) ? Math.ceil(from) : Math.floor(from); if (from < 0) from += len; for (; from < len; from++) { if (from in this && this[from] === elt) return from; } return -1; }; } Example Try the following example. <html> <head> <title>JavaScript Array indexOf Method</title> </head> <body> <script type="text/javascript"> if (!Array.prototype.indexOf) { Array.prototype.indexOf = function(elt /*, from*/) { var len = this.length; 192 Javascript var from = Number(arguments[1]) || 0; from = (from < 0) ? Math.ceil(from) : Math.floor(from); if (from < 0) from += len; for (; from < len; from++) { if (from in this && this[from] === elt) return from; } return -1; }; } function printBr(element, index, array) { document.write("<br />[" + index + "] is " + element ); } var index = [12, 5, 8, 130, 44].indexOf(8); document.write("index is : " + index ); var index = [12, 5, 8, 130, 44].indexOf(13); document.write("<br />index is : " + index ); </script> </body> </html> Output index is : 2 index is : -1 193 Javascript join () Javascript array join() method joins all the elements of an array into a string. Syntax Its syntax is as follows: array.join(separator); Parameter Details separator : Specifies a string to separate each element of the array. If omitted, the array elements are separated with a comma. Return Value Returns a string after joining all the array elements. Example Try the following example. <html> <head> <title>JavaScript Array join Method</title> </head> <body> <script type="text/javascript"> var arr = new Array("First","Second","Third"); var str = arr.join(); document.write("str : " + str ); var str = arr.join(", "); document.write("<br />str : " + str ); var str = arr.join(" + "); document.write("<br />str : " + str ); </script> </body> 194 Javascript </html> Output str : First,Second,Third str : First, Second, Third str : First + Second + Third lastIndexOf () Javascript array lastIndexOf() method returns the last index at which a given element can be found in the array, or -1 if it is not present. The array is searched backwards, starting at fromIndex. Syntax Its syntax is as follows: array.join(separator); Parameter Details   searchElement : Element to locate in the array. fromIndex : The index at which to start searching backwards. Defaults to the array's length, i.e., the whole array will be searched. If the index is greater than or equal to the length of the array, the whole array will be searched. If negative, it is taken as the offset from the end of the array. Return Value Returns the index of the found element from the last. Compatibility This method is a JavaScript extension to the ECMA-262 standard; as such it may not be present in other implementations of the standard. To make it work, you need to add the following code at the top of your script. if (!Array.prototype.lastIndexOf) { Array.prototype.lastIndexOf = function(elt /*, from*/) { var len = this.length; 195 Javascript var from = Number(arguments[1]); if (isNaN(from)) { from = len - 1; } else { from = (from < 0) ? Math.ceil(from) : Math.floor(from); if (from < 0) from += len; else if (from >= len) from = len - 1; } for (; from > -1; from--) { if (from in this && this[from] === elt) return from; } return -1; }; } Example Try the following example. <html> <head> <title>JavaScript Array lastIndexOf Method</title> 196 Javascript </head> <body> <script type="text/javascript"> if (!Array.prototype.lastIndexOf) { Array.prototype.lastIndexOf = function(elt /*, from*/) { var len = this.length; var from = Number(arguments[1]); if (isNaN(from)) { from = len - 1; } else { from = (from < 0) ? Math.ceil(from) : Math.floor(from); if (from < 0) from += len; else if (from >= len) from = len - 1; } for (; from > -1; from--) { if (from in this && this[from] === elt) return from; } return -1; }; 197 Javascript } var index = [12, 5, 8, 130, 44].lastIndexOf(8); document.write("index is : " + index ); var index = [12, 5, 8, 130, 44, 5].lastIndexOf(5); document.write("<br />index is : " + index ); </script> </body> </html> Output index is : 2 index is : 5 map () Javascript array map() method creates a new array with the results of calling a provided function on every element in this array. Syntax Its syntax is as follows: array.map(callback[, thisObject]); Parameter Details   callback : Function that produces an element of the new Array from an element of the current one. thisObject : Object to use as this when executing callback. Return Value Returns the created array. Compatibility 198 Javascript This method is a JavaScript extension to the ECMA-262 standard; as such it may not be present in other implementations of the standard. To make it work, you need to add the following code at the top of your script. if (!Array.prototype.map) { Array.prototype.map = function(fun /*, thisp*/) { var len = this.length; if (typeof fun != "function") throw new TypeError(); var res = new Array(len); var thisp = arguments[1]; for (var i = 0; i < len; i++) { if (i in this) res[i] = fun.call(thisp, this[i], i, this); } return res; }; } Example Try the following example. <html> <head> <title>JavaScript Array map Method</title> </head> <body> <script type="text/javascript"> if (!Array.prototype.map) { 199 Javascript Array.prototype.map = function(fun /*, thisp*/) { var len = this.length; if (typeof fun != "function") throw new TypeError(); var res = new Array(len); var thisp = arguments[1]; for (var i = 0; i < len; i++) { if (i in this) res[i] = fun.call(thisp, this[i], i, this); } return res; }; } var numbers = [1, 4, 9]; var roots = numbers.map(Math.sqrt); document.write("roots is : " + roots ); </script> </body> </html> Output roots is : 1,2,3 pop () Javascript array pop() method removes the last element from an array and returns that element. 200 Javascript Syntax Its syntax is as follows: Array.pop(); Return Value Returns the removed element from the array. Example Try the following example. <html> <head> <title>JavaScript Array pop Method</title> </head> <body> <script type="text/javascript"> var numbers = [1, 4, 9]; var element = numbers.pop(); document.write("element is : " + element ); var element = numbers.pop(); document.write("<br />element is : " + element ); </script> </body> </html> Output element is : 9 element is : 4 push () Javascript array push() method appends the given element(s) in the last of the array and returns the length of the new array. Syntax 201 Javascript Its syntax is as follows: Array.push(); Parameter Details element1, ..., elementN: The elements to add to the end of the array. Return Value Returns the length of the new array. Example Try the following example. <html> <head> <title>JavaScript Array push Method</title> </head> <body> <script type="text/javascript"> var numbers = new Array(1, 4, 9); var length = numbers.push(10); document.write("new numbers is : " + numbers ); length = numbers.push(20); document.write("<br />new numbers is : " + numbers ); </script> </body> </html> Output new numbers is : 1,4,9,10 new numbers is : 1,4,9,10,20 202 Javascript reduce () Javascript array reduce() method applies a function simultaneously against two values of the array (from left-to-right) as to reduce it to a single value. Syntax Its syntax is as follows: array.reduce(callback[, initialValue]); Parameter Details   callback : Function to execute on each value in the array. initialValue : Object to use as the first argument to the first call of the callback. Return Value Returns the reduced single value of the array. Compatibility This method is a JavaScript extension to the ECMA-262 standard; as such it may not be present in other implementations of the standard. To make it work, you need to add the following code at the top of your script. if (!Array.prototype.reduce) { Array.prototype.reduce = function(fun /*, initial*/) { var len = this.length; if (typeof fun != "function") throw new TypeError(); // no value to return if no initial value and an empty array if (len == 0 && arguments.length == 1) throw new TypeError(); var i = 0; if (arguments.length >= 2) { 203 Javascript var rv = arguments[1]; } else { do { if (i in this) { rv = this[i++]; break; } // if array contains no values, no initial value to return if (++i >= len) throw new TypeError(); } while (true); } for (; i < len; i++) { if (i in this) rv = fun.call(null, rv, this[i], i, this); } return rv; }; } Example Try the following example. <html> <head> 204 Javascript <title>JavaScript Array reduce Method</title> </head> <body> <script type="text/javascript"> if (!Array.prototype.reduce) { Array.prototype.reduce = function(fun /*, initial*/) { var len = this.length; if (typeof fun != "function") throw new TypeError(); // no value to return if no initial value and an empty array if (len == 0 && arguments.length == 1) throw new TypeError(); var i = 0; if (arguments.length >= 2) { var rv = arguments[1]; } else { do { if (i in this) { rv = this[i++]; break; } // if array contains no values, no initial value to return if (++i >= len) 205 Javascript throw new TypeError(); } while (true); } for (; i < len; i++) { if (i in this) rv = fun.call(null, rv, this[i], i, this); } return rv; }; } var total = [0, 1, 2, 3].reduce(function(a, b){ return a + b; }); document.write("total is : " + total ); </script> </body> </html> Output total is : 6 reduceRight () Javascript array reduceRight() method applies a function simultaneously against two values of the array (from right-to-left) as to reduce it to a single value. Syntax Its syntax is as follows: array.reduceRight(callback[, initialValue]); Parameter Details 206 Javascript   callback : Function to execute on each value in the array. initialValue : Object to use as the first argument to the first call of the callback. Return Value Returns the reduced right single value of the array. Compatibility This method is a JavaScript extension to the ECMA-262 standard; as such it may not be present in other implementations of the standard. To make it work, you need to add the following code at the top of your script. if (!Array.prototype.reduceRight) { Array.prototype.reduceRight = function(fun /*, initial*/) { var len = this.length; if (typeof fun != "function") throw new TypeError(); // no value to return if no initial value, empty array if (len == 0 && arguments.length == 1) throw new TypeError(); var i = len - 1; if (arguments.length >= 2) { var rv = arguments[1]; } else { do { if (i in this) { 207 Javascript rv = this[i--]; break; } // if array contains no values, no initial value to return if (--i < 0) throw new TypeError(); } while (true); } for (; i >= 0; i--) { if (i in this) rv = fun.call(null, rv, this[i], i, this); } return rv; }; } Example Try the following example. <html> <head> <title>JavaScript Array reduceRight Method</title> </head> <body> <script type="text/javascript"> if (!Array.prototype.reduceRight) { Array.prototype.reduceRight = function(fun /*, initial*/) { 208 Javascript var len = this.length; if (typeof fun != "function") throw new TypeError(); // no value to return if no initial value, empty array if (len == 0 && arguments.length == 1) throw new TypeError(); var i = len - 1; if (arguments.length >= 2) { var rv = arguments[1]; } else { do { if (i in this) { rv = this[i--]; break; } // if array contains no values, no initial value to return if (--i < 0) throw new TypeError(); } while (true); } for (; i >= 0; i--) { if (i in this) 209 Javascript rv = fun.call(null, rv, this[i], i, this); } return rv; }; } var total = [0, 1, 2, 3].reduceRight(function(a, b){ return a + b; }); document.write("total is : " + total ); </script> </body> </html> Output total is : 6 reverse () Javascript array reverse() method reverses the element of an array. The first array element becomes the last and the last becomes the first. Syntax Its syntax is as follows: array.reverse(); Return Value Returns the reversed single value of the array. Example Try the following example. <html> <head> <title>JavaScript Array reverse Method</title> </head> 210 Javascript <body> <script type="text/javascript"> var arr = [0, 1, 2, 3].reverse(); document.write("Reversed array is : " + arr ); </script> </body> </html> Output Reversed array is : 3,2,1,0 shift () Javascript array shift() method removes the first element from an array and returns that element. Syntax Its syntax is as follows: array.shift(); Return Value Returns the removed single value of the array. Example Try the following example. <html> <head> <title>JavaScript Array shift Method</title> </head> <body> <script type="text/javascript"> var element = [105, 1, 2, 3].shift(); document.write("Removed element is : " + element ); </script> </body> 211 Javascript </html> Output Removed element is : 105 slice () Javascript array slice() method extracts a section of an array and returns a new array. Syntax Its syntax is as follows: array.slice( begin [,end] ); Parameter Details   begin : Zero-based index at which to begin extraction. As a negative index, start indicates an offset from the end of the sequence. end : Zero-based index at which to end extraction. Return Value Returns the extracted array based on the passed parameters. Example Try the following example. <html> <head> <title>JavaScript Array slice Method</title> </head> <body> <script type="text/javascript"> var arr = ["orange", "mango", "banana", "sugar", "tea"]; document.write("arr.slice( 1, 2) : " + arr.slice( 1, 2) ); document.write("<br />arr.slice( 1, 2) : " + arr.slice( 1, 3) ); </script> </body> 212 Javascript </html> Output arr.slice( 1, 2) : mango arr.slice( 1, 2) : mango,banana some () Javascript array some() method tests whether some element in the array passes the test implemented by the provided function. Syntax Its syntax is as follows: array.some(callback[, thisObject]); Parameter Details   callback : Function to test for each element. thisObject : Object to use as this when executing callback. Return Value If some element pass the test, then it returns true, otherwise false. Compatibility This method is a JavaScript extension to the ECMA-262 standard; as such it may not be present in other implementations of the standard. To make it work, you need to add the following code at the top of your script. if (!Array.prototype.some) { Array.prototype.some = function(fun /*, thisp*/) { var len = this.length; if (typeof fun != "function") throw new TypeError(); var thisp = arguments[1]; for (var i = 0; i < len; i++) 213 Javascript { if (i in this && fun.call(thisp, this[i], i, this)) return true; } return false; }; } Example Try the following example. <html> <head> <title>JavaScript Array some Method</title> </head> <body> <script type="text/javascript"> if (!Array.prototype.some) { Array.prototype.some = function(fun /*, thisp*/) { var len = this.length; if (typeof fun != "function") throw new TypeError(); var thisp = arguments[1]; for (var i = 0; i < len; i++) { if (i in this && fun.call(thisp, this[i], i, this)) return true; } 214 Javascript return false; }; } function isBigEnough(element, index, array) { return (element >= 10); } var retval = [2, 5, 8, 1, 4].some(isBigEnough); document.write("Returned value is : " + retval ); var retval = [12, 5, 8, 1, 4].some(isBigEnough); document.write("<br />Returned value is : " + retval ); </script> </body> </html> Output Returned value is : false Returned value is : true sort () Javascript array sort() method sorts the elements of an array. Syntax Its syntax is as follows: array.sort( compareFunction ); Parameter Details compareFunction: Specifies a function that defines the sort order. If omitted, the array is sorted lexicographically. 215 Javascript Return Value Returns a sorted array. Example Try the following example. <html> <head> <title>JavaScript Array sort Method</title> </head> <body> <script type="text/javascript"> var arr = new Array("orange", "mango", "banana", "sugar"); var sorted = arr.sort(); document.write("Returned string is : " + sorted ); </script> </body> </html> Output Returned string is : banana,mango,orange,sugar splice () Javascript array splice() method changes the content of an array, adding new elements while removing old elements. Syntax Its syntax is as follows: array.splice(index, howMany, [element1][, ..., elementN]); Parameter Details  index: Index at which to start changing the array. 216 Javascript   howMany: An integer indicating the number of old array elements to remove. If howMany is 0, no elements are removed. element1, ..., elementN: The elements to add to the array. If you don't specify any elements, splice simply removes the elements from the array. Return Value Returns the extracted array based on the passed parameters. Example Try the following example. <html> <head> <title>JavaScript Array splice Method</title> </head> <body> <script type="text/javascript"> var arr = ["orange", "mango", "banana", "sugar", "tea"]; var removed = arr.splice(2, 0, "water"); document.write("After adding 1: " + arr ); document.write("<br />removed is: " + removed); removed = arr.splice(3, 1); document.write("<br />After adding 1: " + arr ); document.write("<br />removed is: " + removed); </script> </body> </html> Output After adding 1: orange,mango,water,banana,sugar,tea removed is: After adding 1: orange,mango,water,sugar,tea removed is: banana 217 Javascript toString () Javascript array toString() method returns a string representing the source code of the specified array and its elements. Syntax Its syntax is as follows: array.toString( ); Return Value Returns a string representing the array. Example Try the following example. <html> <head> <title>JavaScript Array toString Method</title> </head> <body> <script type="text/javascript"> var arr = new Array("orange", "mango", "banana", "sugar"); var str = arr.toString(); document.write("Returned string is : " + str ); </script> </body> </html> Output Returned string is : orange,mango,banana,sugar unshift () Javascript array unshift() method adds one or more elements to the beginning of an array and returns the new length of the array. 218 Javascript Syntax Its syntax is as follows: array.unshift( element1, ..., elementN ); Parameter Details element1, ..., elementN : The elements to add to the front of the array. Return Value Returns the length of the new array. It returns undefined in IE browser. Example Try the following example. <html> <head> <title>JavaScript Array unshift Method</title> </head> <body> <script type="text/javascript"> var arr = new Array("orange", "mango", "banana", "sugar"); var length = arr.unshift("water"); document.write("Returned array is : " + arr ); document.write("<br /> Length of the array is : " + length ); </script> </body> </html> Output Returned array is : water,orange,mango,banana,sugar Length of the array is : 5 219 25. DATE Javascript The Date object is a datatype built into the JavaScript language. Date objects are created with the new Date() as shown below. Once a Date object is created, a number of methods allow you to operate on it. Most methods simply allow you to get and set the year, month, day, hour, minute, second, and millisecond fields of the object, using either local time or UTC (universal, or GMT) time. The ECMAScript standard requires the Date object to be able to represent any date and time, to millisecond precision, within 100 million days before or after 1/1/1970. This is a range of plus or minus 273,785 years, so JavaScript can represent date and time till the year 275755. Syntax You can use any of the following syntaxes to create a Date object using Date() constructor. new Date( ) new Date(milliseconds) new Date(datestring) new Date(year,month,date[,hour,minute,second,millisecond ]) Note: Parameters in the brackets are always optional. Here is a description of the parameters:     No Argument: With no arguments, the Date() constructor creates a Date object set to the current date and time. milliseconds: When one numeric argument is passed, it is taken as the internal numeric representation of the date in milliseconds, as returned by the getTime() method. For example, passing the argument 5000 creates a date that represents five seconds past midnight on 1/1/70. datestring: When one string argument is passed, it is a string representation of a date, in the format accepted by the Date.parse() method. 7 agruments: To use the last form of the constructor shown above. Here is a description of each argument: 220 Javascript o year: Integer value representing the year. For compatibility (in order to avoid the Y2K problem), you should always specify the year in full; use 1998, rather than 98. o month: Integer value representing the month, beginning with 0 for January to 11 for December. o date: Integer value representing the day of the month. o hour: Integer value representing the hour of the day (24-hour scale). o minute: Integer value representing the minute segment of a time reading. o second: Integer value representing the second segment of a time reading. o millisecond: Integer value representing the millisecond segment of a time reading. Date Properties Here is a list of the properties of the Date object along with their description. Property Description constructor Specifies the prototype. prototype The prototype property allows you to add properties and methods to an object. function that creates an object's In the following sections, we will have a few examples to demonstrate the usage of different Date properties. constructor Javascript date constructor property returns a reference to the array function that created the instance's prototype. Syntax Its syntax is as follows: date.constructor 221 Javascript Return Value Returns the function that created this object's instance. Example Try the following example. <html> <head> <title>JavaScript Date constructor Property</title> </head> <body> <script type="text/javascript"> var dt = new Date(); document.write("dt.constructor is : " + dt.constructor); </script> </body> </html> Output dt.constructor is : function Date() { [native code] } Prototype The prototype property allows you to add properties and methods to any object (Number, Boolean, String, Date, etc.). Note: Prototype is a global property which is available with almost all the objects. Syntax Its syntax is as follows: object.prototype.name = value 222 Javascript Example Try the following example. <html> <head> <title>User-defined objects</title> <script type="text/javascript"> function book(title, author){ this.title = title; this.author = author; } </script> </head> <body> <script type="text/javascript"> var myBook = new book("Perl", "Mohtashim"); book.prototype.price = null; myBook.price = 100; document.write("Book title is : " + myBook.title + "<br>"); document.write("Book author is : " + myBook.author + "<br>"); document.write("Book price is : " + myBook.price + "<br>"); </script> </body> </html> Output Book title is : Perl Book author is : Mohtashim Book price is : 100 223 Javascript Date Methods Here is a list of the methods used with Date and their description. Method Description Date() Returns today's date and time getDate() Returns the day of the month for the specified date according to local time. getDay() Returns the day of the week for the specified date according to local time. getFullYear() Returns the year of the specified date according to local time. getHours() Returns the hour in the specified date according to local time. getMilliseconds() Returns the milliseconds in the specified date according to local time. getMinutes() Returns the minutes in the specified date according to local time. getMonth() Returns the month in the specified date according to local time. getSeconds() Returns the seconds in the specified date according to local time. getTime() Returns the numeric value of the specified date as the number of milliseconds since January 1, 1970, 00:00:00 UTC. getTimezoneOffset() Returns the time-zone offset in minutes for the current locale. getUTCDate() Returns the day (date) of the month in the specified date according to universal time. getUTCDay() Returns the day of the week in the specified date according to universal time. getUTCFullYear() Returns the year in the specified date according to universal time. getUTCHours() Returns the hours in the specified date according to universal time. getUTCMilliseconds() Returns the milliseconds in the specified date 224 Javascript according to universal time. getUTCMinutes() Returns the minutes in the specified date according to universal time. getUTCMonth() Returns the month in the specified date according to universal time. getUTCSeconds() Returns the seconds in the specified date according to universal time. getYear() Deprecated - Returns the year in the specified date according to local time. Use getFullYear instead. setDate() Sets the day of the month for a specified date according to local time. setFullYear() Sets the full year for a specified date according to local time. setHours() Sets the hours for a specified date according to local time. setMilliseconds() Sets the milliseconds for a specified date according to local time. setMinutes() Sets the minutes for a specified date according to local time. setMonth() Sets the month for a specified date according to local time. setSeconds() Sets the seconds for a specified date according to local time. setTime() Sets the Date object to the time represented by a number of milliseconds since January 1, 1970, 00:00:00 UTC. setUTCDate() Sets the day of the month for a specified date according to universal time. setUTCFullYear() Sets the full year for a specified date according to universal time. setUTCHours() Sets the hour for a specified date according to universal time. setUTCMilliseconds() Sets the milliseconds for a specified date according to universal time. setUTCMinutes() Sets the minutes for a specified date according to 225 Javascript universal time. setUTCMonth() Sets the month for a specified date according to universal time. setUTCSeconds() Sets the seconds for a specified date according to universal time. setYear() Deprecated - Sets the year for a specified date according to local time. Use setFullYear instead. toDateString() Returns the "date" portion of the Date as a humanreadable string. toGMTString() Deprecated - Converts a date to a string, using the Internet GMT conventions. Use toUTCString instead. toLocaleDateString() Returns the "date" portion of the Date as a string, using the current locale's conventions. toLocaleFormat() Converts a date to a string, using a format string. toLocaleString() Converts a date to a string, using the current locale's conventions. toLocaleTimeString() Returns the "time" portion of the Date as a string, using the current locale's conventions. toSource() Returns a string representing the source for an equivalent Date object; you can use this value to create a new object. toString() Returns a string representing the specified Date object. toTimeString() Returns the "time" portion of the Date as a humanreadable string. toUTCString() Converts a date to a string, using the universal time convention. valueOf() Returns the primitive value of a Date object. In the following sections, we will have a few examples to demonstrate the usage of Date methods. 226 Javascript Date() Javascript Date() method returns today's date and time and does not need any object to be called. Syntax Its syntax is as follows: Date() Return Value Returns today's date and time. Example Try the following example. <html> <head> <title>JavaScript Date Method</title> </head> <body> <script type="text/javascript"> var dt = Date(); document.write("Date and Time : " + dt ); </script> </body> </html> Output Date and Time : Wed Mar 25 2015 15:00:57 GMT+0530 (India Standard Time) getDate() Javascript date getDate() method returns the day of the month for the specified date according to local time. The value returned by getDate is an integer between 1 and 31. 227 Javascript Syntax Its syntax is as follows: Date.getDate() Return Value Returns today's date and time. Example Try the following example. <html> <head> <title>JavaScript getDate Method</title> </head> <body> <script type="text/javascript"> var dt = new Date("December 25, 1995 23:15:00"); document.write("getDate() : " + dt.getDate() ); </script> </body> </html> Output getDate() : 25 getDay() Javascript date getDay() method returns the day of the week for the specified date according to local time. The value returned by getDay is an integer corresponding to the day of the week: 0 for Sunday, 1 for Monday, 2 for Tuesday, and so on. Syntax Its syntax is as follows: Date.getDay() 228 Javascript Return Value Returns the day of the week for the specified date according to local time. Example Try the following example. <html> <head> <title>JavaScript getDay Method</title> </head> <body> <script type="text/javascript"> var dt = new Date("December 25, 1995 23:15:00"); document.write("getDay() : " + dt.getDay() ); </script> </body> </html> Output getDay() : 1 getFullYear() Javascript date getFullYear() method returns the year of the specified date according to local time. The value returned by getFullYear is an absolute number. For dates between the years 1000 and 9999, getFullYear returns a four-digit number, for example, 2008. Syntax Its syntax is as follows: Date.getFullYear() Return Value Returns the year of the specified date according to local time. 229 Javascript Example Try the following example. <html> <head> <title>JavaScript getFullYear Method</title> </head> <body> <script type="text/javascript"> var dt = new Date("December 25, 1995 23:15:00"); document.write("getFullYear() : " + dt.getFullYear() ); </script> </body> </html> Output getFullYear() : 1995 getHours() Javascript Date getHours() method returns the hour in the specified date according to local time. The value returned by getHours is an integer between 0 and 23. Syntax Its syntax is as follows: Date.getHours() Return Value Returns the hour in the specified date according to local time. Example 230 Javascript Try the following example. <html> <head> <title>JavaScript getHours Method</title> </head> <body> <script type="text/javascript"> var dt = new Date("December 25, 1995 23:15:00"); document.write("getHours() : " + dt.getHours() ); </script> </body> </html> Output getHours() : 23 getMilliseconds() Javascript date getMilliseconds() method returns the milliseconds in the specified date according to local time. The value returned by getMilliseconds is a number between 0 and 999. Syntax Its syntax is as follows: Date.getMilliseconds () Return Value Returns the milliseconds in the specified date according to local time. Example Try the following example. <html> <head> <title>JavaScript getMilliseconds Method</title> </head> 231 Javascript <body> <script type="text/javascript"> var dt = new Date(); document.write("getMilliseconds() : " + dt.getMilliseconds() ); </script> </body> </html> Output getMilliseconds() : 641 getMinutes () Javascript date getMinutes() method returns the minutes in the specified date according to local time. The value returned by getMinutes is an integer between 0 and 59. Syntax Its syntax is as follows: Date.getMinutes () Return Value Returns the minutes in the specified date according to local time. Example Try the following example. <html> <head> <title>JavaScript getMinutes Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "December 25, 1995 23:15:00" ); document.write("getMinutes() : " + dt.getMinutes() ); </script> 232 Javascript </body> </html> Output getMinutes() : 15 getMonth () Javascript date getMonth() method returns the month in the specified date according to local time. The value returned by getMonth is an integer between 0 and 11. 0 corresponds to January, 1 to February, and so on. Syntax Its syntax is as follows: Date.getMonth () Return Value Returns the Month in the specified date according to local time. Example Try the following example. <html> <head> <title>JavaScript getMonth Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "December 25, 1995 23:15:00" ); document.write("getMonth() : " + dt.getMonth() ); </script> </body> </html> Output 233 Javascript getMonth() : 11 getSeconds () Javascript date getSeconds() method returns the seconds in the specified date according to local time. The value returned by getSeconds is an integer between 0 and 59. Syntax Its syntax is as follows: Date.getSeconds () Return Value Returns the seconds in the specified date according to local time. Example Try the following example. <html> <head> <title>JavaScript getSeconds Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "December 25, 1995 23:15:20" ); document.write("getSeconds() : " + dt.getSeconds() ); </script> </body> </html> Output getSeconds () : 20 getTime () Javascript date getTime() method returns the numeric value corresponding to the time for the specified date according to universal time. The value returned 234 Javascript by the getTime method is the number of milliseconds since 1 January 1970 00:00:00. You can use this method to help assign a date and time to another Date object. Syntax Its syntax is as follows: Date.getTime () Return Value Returns the numeric value corresponding to the time for the specified date according to universal time. Example Try the following example. <html> <head> <title>JavaScript getTime Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "December 25, 1995 23:15:20" ); document.write("getTime() : " + dt.getTime() ); </script> </body> </html> Output getTime() : 819913520000 getTimezoneOffset () Javascript date getTimezoneOffset() method returns the time-zone offset in minutes for the current locale. The time-zone offset is the minutes in difference, the Greenwich Mean Time (GMT) is relative to your local time. For example, if your time zone is GMT+10, -600 will be returned. Daylight savings time prevents this value from being a constant. 235 Javascript Syntax Its syntax is as follows: Date.getTimezoneOffset () Return Value Returns the time-zone offset in minutes for the current locale. Example Try the following example. <html> <head> <title>JavaScript getTimezoneOffset Method</title> </head> <body> <script type="text/javascript"> var dt = new Date(); var tz = dt.getTimezoneOffset(); document.write("getTimezoneOffset() : " + tz ); </script> </body> </html> Output getTimezoneOffset() : -330 getUTCDate () Javascript date getUTCDate() method returns the day of the month in the specified date according to universal time. The value returned by getUTCDate is an integer between 1 and 31. Syntax Its syntax is as follows: Date.getUTCDate () 236 Javascript Return Value Returns the day of the month in the specified date according to universal time. Example Try the following example. <html> <head> <title>JavaScript getUTCDate Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "December 25, 1995 23:15:20" ); document.write("getUTCDate() : " + dt.getUTCDate() ); </script> </body> </html> Output getUTCDate() : 25 getUTCDay () Javascript date getUTCDay() method returns the day of the week in the specified date according to universal time. The value returned by getUTCDay is an integer corresponding to the day of the week: 0 for Sunday, 1 for Monday, 2 for Tuesday, and so on. Syntax Its syntax is as follows: Date.getUTCDay () Return Value Returns the day of the week in the specified date according to universal time. Example 237 Javascript Try the following example. <html> <head> <title>JavaScript getUTCDay Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "December 25, 1995 23:15:20" ); document.write("getUTCDay() : " + dt.getUTCDay() ); </script> </body> </html> Output getUTCDay() : 1 getUTCFullYear () Javascript date getUTCFullYear() method returns the year in the specified date according to universal time. The value returned by getUTCFullYear is an absolute number that is compliant with year-2000, for example, 2008. Syntax Its syntax is as follows: Date.getUTCFullYear () Return Value Returns the year in the specified date according to universal time. Example Try the following example. <html> <head> <title>JavaScript getUTCFullYear Method</title> </head> 238 Javascript <body> <script type="text/javascript"> var dt = new Date( "December 25, 1995 23:15:20" ); document.write("getUTCFullYear() : " + dt.getUTCFullYear() ); </script> </body> </html> Output getUTCFullYear() : 1995 getUTCHours () Javascript date getUTCHours() method returns the hours in the specified date according to universal time. The value returned by getUTCHours is an integer between 0 and 23. Syntax Its syntax is as follows: Date.getUTCHours () Return Value Returns the hours in the specified date according to universal time. Example Try the following example. <html> <head> <title>JavaScript getUTCHours Method</title> </head> <body> <script type="text/javascript"> var dt = new Date(); document.write("getUTCHours() : " + dt.getUTCHours() ); </script> 239 Javascript </body> </html> Output getUTCHours() : 11 getUTCMilliseconds () Javascript date getUTCMilliseconds() method returns the milliseconds in the specified date according to universal time. The value returned by getUTCMilliseconds is an integer between 0 and 999. Syntax Its syntax is as follows: Date.getUTCMilliseconds () Return Value Returns the milliseconds in the specified date according to universal time. Example Try the following example. <html> <head> <title>JavaScript getUTCMilliseconds Method</title> </head> <body> <script type="text/javascript"> var dt = new Date(); document.write("getUTCMilliseconds() : " + dt.getUTCMilliseconds() ); </script> </body> </html> Output getUTCMilliseconds() : 206 240 Javascript getUTCMinutes () Javascript date getUTCMinutes() method returns the minutes in the specified date according to universal time. The value returned by getUTCMinutes is an integer between 0 and 59. Syntax Its syntax is as follows: Date.getUTCMinutes () Return Value Returns the minutes in the specified date according to universal time. Example Try the following example. <html> <head> <title>JavaScript getUTCMinutes Method</title> </head> <body> <script type="text/javascript"> var dt = new Date(); document.write("getUTCMinutes() : " + dt.getUTCMinutes() ); </script> </body> </html> Output getUTCMinutes() : 18 getUTCMonth () Javascript date getUTCMonth() method returns the month in the specified date according to universal time. The value returned by getUTCMonth is an integer between 0 and 11 corresponding to the month. 0 for January, 1 for February, 2 for March, and so on. 241 Javascript Syntax Its syntax is as follows: Date.getUTCMonth () Return Value Returns the month in the specified date according to universal time. Example Try the following example. <html> <head> <title>JavaScript getUTCMonth Method</title> </head> <body> <script type="text/javascript"> var dt = new Date(); document.write("getUTCMonth() : " + dt.getUTCMonth() ); </script> </body> </html> Output getUTCMonth() : 2 getUTCSeconds () Javascript date getUTCSeconds() method returns the seconds in the specified date according to universal time. The value returned by getUTCSeconds is an integer between 0 and 59. Syntax Its syntax is as follows: Date.getUTCSeconds () Return Value Returns the month in the specified date according to universal time. 242 Javascript Example Try the following example. <html> <head> <title>JavaScript getUTCSeconds Method</title> </head> <body> <script type="text/javascript"> var dt = new Date(); document.write("getUTCSeconds() : " + dt.getUTCSeconds() ); </script> </body> </html> Output getUTCSeconds() : 24 getYear () Javascript date getYear() method returns the year in the specified date according to universal time. The getYear is no longer used and has been replaced by the getFullYear method. The value returned by getYear is the current year minus 1900. JavaScript 1.2 and earlier versions return either a 2-digit or 4-digit year. For example, if the year is 2026, the value returned is 2026. So before testing this function, you need to be sure of the javascript version you are using. Syntax Its syntax is as follows: Date.getYear () Return Value Returns the year in the specified date according to universal time. Example Try the following example. 243 Javascript <html> <head> <title>JavaScript getYear Method</title> </head> <body> <script type="text/javascript"> var dt = new Date(); document.write("getYear() : " + dt.getYear() ); </script> </body> </html> Output getYear() : 115 setDate () Javascript date setDate() method sets the day of the month for a specified date according to local time. Syntax Its syntax is as follows: Date.setDate( dayValue ) Parameter Detail dayValue : An integer from 1 to 31, representing the day of the month. Example Try the following example. <html> <head> <title>JavaScript setDate Method</title> </head> <body> <script type="text/javascript"> 244 Javascript var dt = new Date( "Aug 28, 2008 23:30:00" ); dt.setDate( 24 ); document.write( dt ); </script> </body> </html> Output Sun Aug 24 2008 23:30:00 GMT+0530 (India Standard Time) setFullYear () Javascript date setFullYear() method sets the full year for a specified date according to local time. Syntax Its syntax is as follows: Date.setFullYear(yearValue[, monthValue[, dayValue]]) Parameter Detail    yearValue : An integer specifying the numeric value of the year, for example, 2008. monthValue : An integer between 0 and 11 representing the months January through December. dayValue : An integer between 1 and 31 representing the day of the month. If you specify the dayValue parameter, you must also specify the monthValue. If you do not specify the monthValue and dayValue parameters, the values returned from the getMonth and getDate methods are used. Example Try the following example. <html> 245 Javascript <head> <title>JavaScript setFullYear Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "Aug 28, 2008 23:30:00" ); dt.setFullYear( 2000 ); document.write( dt ); </script> </body> </html> Output Mon Aug 28 2000 23:30:00 GMT+0530 (India Standard Time) setHours () Javascript date setHours() method sets the hours for a specified date according to local time. Syntax Its syntax is as follows: Date.setHours(hoursValue[, minutesValue[, secondsValue[, msValue]]]) Note: Parameters in the bracket are always optional. Parameter Detail     hoursValue : An integer between 0 and 23, representing the hour. minutesValue : An integer between 0 and 59, representing the minutes. secondsValue : An integer between 0 and 59, representing the seconds. If you specify the secondsValue parameter, you must also specify the minutesValue. msValue : A number between 0 and 999, representing the milliseconds. If you specify the msValue parameter, you must also specify the minutesValue and secondsValue. 246 Javascript If you do not specify the minutesValue, secondsValue, and msValue parameters, the values returned from the getUTCMinutes, getUTCSeconds, and getMilliseconds methods are used. Example Try the following example. <html> <head> <title>JavaScript setHours Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "Aug 28, 2008 23:30:00" ); dt.setHours( 02 ); document.write( dt ); </script> </body> </html> Output Thu Aug 28 2008 02:30:00 GMT+0530 (India Standard Time) setMilliseconds () Javascript date setMilliseconds() method sets the milliseconds for a specified date according to local time. Syntax Its syntax is as follows: Date.setMilliseconds(millisecondsValue) Note: Parameters in the bracket are always optional. Parameter Detail millisecondsValue : milliseconds. A number between 0 and 999, representing the 247 Javascript If you specify a number outside the expected range, the date information in the Date object is updated accordingly. For example, if you specify 1010, the number of seconds is incremented by 1, and 10 is used for the milliseconds. Example Try the following example. <html> <head> <title>JavaScript setMilliseconds Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "Aug 28, 2008 23:30:00" ); dt.setMilliseconds( 1010 ); document.write( dt ); </script> </body> </html> Output Thu Aug 28 2008 23:30:01 GMT+0530 (India Standard Time) setMinutes () Javascript date setMinutes() method sets the minutes for a specified date according to local time. Syntax Its syntax is as follows: Date.setMinutes(minutesValue[, secondsValue[, msValue]]) Note: Parameters in the bracket are always optional. Parameter Detail  minutesValue : An integer between 0 and 59, representing the minutes. 248 Javascript   secondsValue : An integer between 0 and 59, representing the seconds. If you specify the secondsValue parameter, you must also specify the minutesValue. msValue : A number between 0 and 999, representing the milliseconds. If you specify the msValue parameter, you must also specify the minutesValue and secondsValue. If you do not specify the secondsValue and msValue parameters, the values returned from getSeconds and getMilliseconds methods are used. Try the following example. <html> <head> <title>JavaScript setMinutes Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "Aug 28, 2008 23:30:00" ); dt.setMinutes( 45 ); document.write( dt ); </script> </body> </html> Output Thu Aug 28 2008 23:45:00 GMT+0530 (India Standard Time) setMonth () Javascript date setMonth() method sets the month for a specified date according to local time. Syntax The following syntax for setMonth () Method. Date.setMonth(monthValue[, dayValue]) Note: Parameters in the bracket are always optional. Parameter Detail 249 Javascript    monthValue : An integer between 0 and 11 (representing the months January through December). dayValue : An integer from 1 to 31, representing the day of the month. msValue : A number between 0 and 999, representing the milliseconds. If you specify the msValue parameter, you must also specify the minutesValue and secondsValue. If you do not specify the dayValue parameter, the value returned from the getDate method is used. If a parameter you specify is outside of the expected range, setMonth attempts to update the date information in the Date object accordingly. For example, if you use 15 for monthValue, the year will be incremented by 1 (year + 1), and 3 will be used for month. Example Try the following example. <html> <head> <title>JavaScript setMonth Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "Aug 28, 2008 23:30:00" ); dt.setMonth( 2 ); document.write( dt ); </script> </body> </html> Output Fri Mar 28 2008 23:30:00 GMT+0530 (India Standard Time) setSeconds () Javascript date setSeconds() method sets the seconds for a specified date according to local time. Syntax 250 Javascript Its syntax is as follows: Date.setSeconds(secondsValue[, msValue]) Note: Parameters in the bracket are always optional. Parameter Detail   secondsValue : An integer between 0 and 59. msValue : A number between 0 and 999, representing the milliseconds. If you do not specify the msValue parameter, the value returned from the getMilliseconds method is used. If a parameter you specify is outside of the expected range, setSeconds attempts to update the date information in the Date object accordingly. For example, if you use 100 for secondsValue, the minutes stored in the Date object will be incremented by 1, and 40 will be used for seconds. Example Try the following example. <html> <head> <title>JavaScript setSeconds Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "Aug 28, 2008 23:30:00" ); dt.setSeconds( 80 ); document.write( dt ); </script> </body> </html> Output Thu Aug 28 2008 23:31:20 GMT+0530 (India Standard Time) 251 Javascript setTime () Javascript date setTime() method sets the Date object to the time represented by a number of milliseconds since January 1, 1970, 00:00:00 UTC. Syntax Its syntax is as follows: Date.setTime(timeValue) Note: Parameters in the bracket are always optional. Parameter Detail timeValue :An integer representing the number of milliseconds since 1 January 1970, 00:00:00 UTC. Example Try the following example. <html> <head> <title>JavaScript setTime Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "Aug 28, 2008 23:30:00" ); dt.setTime( 5000000 ); document.write( dt ); </script> </body> </html> Output Thu Jan 01 1970 06:53:20 GMT+0530 (India Standard Time) setUTCDate () Javascript date setUTCDate() method sets the day of the month for a specified date according to universal time. 252 Javascript Syntax Its syntax is as follows: Date.setUTCDate(dayValue) Note: Parameters in the bracket are always optional. Parameter Detail dayValue : An integer from 1 to 31, representing the day of the month. If a parameter you specify is outside the expected range, setUTCDate attempts to update the date information in the Date object accordingly. Example Try the following example. <html> <head> <title>JavaScript setUTCDate Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "Aug 28, 2008 23:30:00" ); dt.setUTCDate( 20 ); document.write( dt ); </script> </body> </html> Output Wed Aug 20 2008 23:30:00 GMT+0530 (India Standard Time) setUTCFullYear () Javascript date setUTCFullYear() method sets the full year for a specified date according to universal time. Syntax Its syntax is as follows: 253 Javascript Date.setUTCFullYear(yearValue[, monthValue[, dayValue]]) Note: Parameters in the bracket are always optional. Parameter Detail    yearValue : An integer specifying the numeric value of the year, for example, 2008. monthValue : An integer between 0 and 11 representing the months January through December. dayValue : An integer between 1 and 31 representing the day of the month. If you specify the dayValue parameter, you must also specify the monthValue. If you do not specify the monthValue and dayValue parameters, the values returned from the getMonth and getDate methods are used. If a parameter you specify is outside of the expected range, setUTCFullYear attempts to update the other parameters and the date information in the Date object accordingly. For example, if you specify 15 for monthValue, the year is incremented by 1 (year + 1), and 3 is used for the month. Example Try the following example. <html> <head> <title>JavaScript setUTCFullYear Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "Aug 28, 2008 23:30:00" ); dt.setUTCFullYear( 2006 ); document.write( dt ); </script> </body> </html> Output Mon Aug 28 2006 23:30:00 GMT+0530 (India Standard Time) 254 Javascript setUTCHours () Javascript date setUTCHours() method sets the hour for a specified date according to universal time. Syntax Its syntax is as follows: Date.setUTCHours(hoursValue[, minutesValue[, secondsValue[, msValue]]]) Note: Parameters in the bracket are always optional. Parameter Detail     hoursValue : An integer between 0 and 23, representing the hour. minutesValue : An integer between 0 and 59, representing the minutes. secondsValue : An integer between 0 and 59, representing the seconds. If you specify the secondsValue parameter, you must also specify the minutesValue. msValue : A number between 0 and 999, representing the milliseconds. If you specify the msValue parameter, you must also specify the minutesValue and secondsValue. If you do not specify the minutesValue, secondsValue, and msValue parameters, the values returned from the getUTCMinutes, getUTCSeconds, and getUTCMilliseconds methods are used. If a parameter you specify is outside the expected range, setUTCHours attempts to update the date information in the Date object accordingly. For example, if you use 100 for secondsValue, the minutes will be incremented by 1 (min + 1), and 40 will be used for seconds. Example Try the following example. <html> <head> <title>JavaScript setUTCHours Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "Aug 28, 2008 23:30:00" ); dt.setUTCHours( 15 ); 255 Javascript document.write( dt ); </script> </body> </html> Output Thu Aug 28 2008 20:30:00 GMT+0530 (India Standard Time) setUTCMilliseconds () Javascript date setUTCMilliseconds() method sets the milliseconds for a specified date according to universal time. Syntax Its syntax is as follows: Date.setUTCMilliseconds(millisecondsValue) Note: Parameters in the bracket are always optional. Parameter Detail millisecondsValue : milliseconds. A number between 0 and 999, representing the If a parameter you specify is outside the expected range, setUTCMilliseconds attempts to update the date information in the Date object accordingly. For example, if you use 1100 for millisecondsValue, the seconds stored in the Date object will be incremented by 1, and 100 will be used for milliseconds. Example Try the following example. <html> <head> <title>JavaScript setUTCMilliseconds Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "Aug 28, 2008 23:30:00" ); dt.setUTCMilliseconds( 1100 ); 256 Javascript document.write( dt ); </script> </body> </html> Output Thu Aug 28 2008 23:30:01 GMT+0530 (India Standard Time) setUTCMinutes () Javascript date setUTCMinutes() method sets the minutes for a specified date according to universal time. Syntax Its syntax is as follows: Date.setUTCMinutes(minutesValue[, secondsValue[, msValue]]) Note: Parameters in the bracket are always optional. Parameter Detail    minutesValue : An integer between 0 and 59, representing the minutes. secondsValue : An integer between 0 and 59, representing the seconds. If you specify the secondsValue parameter, you must also specify the minutesValue. msValue : A number between 0 and 999, representing the milliseconds. If you specify the msValue parameter, you must also specify the minutesValue and secondsValue. If you do not specify the secondsValue and msValue parameters, the values returned from getUTCSeconds and getUTCMilliseconds methods are used. If a parameter you specify is outside of the expected range, setUTCMinutes attempts to update the date information in the Date object accordingly. For example, if you use 100 for secondsValue, the minutes (minutesValue) will be incremented by 1 (minutesValue + 1), and 40 will be used for seconds. Example 257 Javascript Try the following example. <html> <head> <title>JavaScript setUTCMinutes Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "Aug 28, 2008 13:30:00" ); dt.setUTCMinutes( 65 ); document.write( dt ); </script> </body> </html> Output Thu Aug 28 2008 14:35:00 GMT+0530 (India Standard Time) setUTC Month () Javascript date setUTCMonth ( ) method sets the month for a specified date according to universal time. Syntax The following syntax for setUTCMonth ( ) Method. Date.setUTCMonth ( monthvalue ) Note: Parameters in the bracket are always optional. Parameter Detail monthValue : An integer between 0 and 11, representing the month. Example Try the following example. 258 Javascript <html> <head> <title>JavaScript getUTCSeconds Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "Aug 28, 2008 13:30:00" ); dt.setUTCMonth( 2 ); document.write( dt ); </script> </body> </html> Output Fri Mar 28 2008 13:30:00 GMT+0530 (India Standard Time) setUTCSeconds () Javascript date setUTCSeconds() method sets the seconds for a specified date according to universal time. Syntax Its syntax is as follows: Date.setUTCSeconds(secondsValue[, msValue]) Note: Parameters in the bracket are always optional. Parameter Detail   secondsValue : An integer between 0 and 59, representing the seconds. msValue : A number between 0 and 999, representing the milliseconds. If you do not specify the msValue parameter, the value returned from the getUTCMilliseconds methods is used. If a parameter you specify is outside the expected range, setUTCSeconds attempts to update the date information in the Date object accordingly. For example, if you use 100 for secondsValue, the minutes stored in the Date object will be incremented by 1, and 40 will be used for seconds. 259 Javascript Example Try the following example. <html> <head> <title>JavaScript setUTCSeconds Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "Aug 28, 2008 13:30:00" ); dt.setUTCSeconds( 65 ); document.write( dt ); </script> </body> </html> Output Thu Aug 28 2008 13:31:05 GMT+0530 (India Standard Time) setYear () Javascript date setYear() method sets the year for a specified date according to universal time. Syntax Its syntax is as follows: Date.setYear(yearValue) Note: Parameters in the bracket are always optional. Parameter Detail yearValue: An integer value. Example Try the following example. <html> 260 Javascript <head> <title>JavaScript setYear Method</title> </head> <body> <script type="text/javascript"> var dt = new Date( "Aug 28, 2008 13:30:00" ); dt.setYear( 2000 ); document.write( dt ); </script> </body> </html> Output Mon Aug 28 2000 13:30:00 GMT+0530 (India Standard Time) toDateString () Javascript date toDateString() method returns the date portion of a Date object in human readable form. Syntax Its syntax is as follows: Date.toDateString() Return Value Returns the date portion of a Date object in human readable form. Example Try the following example. <html> <head> <title>JavaScript toDateString Method</title> </head> <body> <script type="text/javascript"> 261 Javascript var dt = new Date(1993, 6, 28, 14, 39, 7); document.write( "Formated Date : " + dt.toDateString() ); </script> </body> </html> Output Formated Date : Wed Jul 28 1993 toGMTString () Javascript date toGMTString() method converts a date to a string, using Internet GMT conventioins. This method is no longer used and has been replaced by the toUTCString method. Syntax Its syntax is as follows: Date.toGMTString() Return Value Returns a date to a string, using Internet GMT conventioins. Example Try the following example. <html> <head> <title>JavaScript toGMTString Method</title> </head> <body> <script type="text/javascript"> var dt = new Date(1993, 6, 28, 14, 39, 7); document.write( "Formated Date : " + dt.toGMTString() ); </script> </body> 262 Javascript </html> Output Formated Date : Wed, 28 Jul 1993 09:09:07 GMT toLocaleDateString () Javascript date toLocaleDateString() method converts a date to a string, returning the "date" portion using the operating system's locale's conventions. Syntax Its syntax is as follows: Date.toGMTString() Return Value Returns a date to a string, using Internet GMT conventioins. Example Try the following example. <html> <head> <title>JavaScript toGMTString Method</title> </head> <body> <script type="text/javascript"> var dt = new Date(1993, 6, 28, 14, 39, 7); document.write( "Formated Date : " + dt.toGMTString() ); </script> </body> </html> Output Formated Date : Wed, 28 Jul 1993 09:09:07 GMT 263 Javascript toLocaleDateString () Javascript date toLocaleDateString() method converts a date to a string, returning the "date" portion using the operating system's locale's conventions. Syntax Its syntax is as follows: Date.toLocaleString() Return Value Returns the "date" portion using the operating system's locale's conventions. Example Try the following example. <html> <head> <title>JavaScript toLocaleDateString Method</title> </head> <body> <script type="text/javascript"> var dt = new Date(1993, 6, 28, 14, 39, 7); document.write( "Formated Date : " + dt.toLocaleDateString() ); </script> </body> </html> Output Formated Date : 7/28/1993 toLocaleFormat () Javascript date toLocaleFormat() method converts a date to a string using the specified formatting. Note: This method may not compatible with all the browsers. 264 Javascript Syntax Its syntax is as follows: Date.toLocaleFormat() Parameter Details formatString: A format string in the same format expected by the strftime() function in C. Return Value Returns the formatted date. Example Try the following example. <html> <head> <title>JavaScript toLocaleFormat Method</title> </head> <body> <script type="text/javascript"> var dt = new Date(1993, 6, 28, 14, 39, 7); document.write( "Formated Date : " + dt.toLocaleFormat( "%A, %B %e, %Y" )); </script> </body> </html> Output Formated Date : Wed Jul 28 1993 14:39:07 GMT+0530 (India Standard Time) toLocaleString () Javascript date toLocaleString() method converts a date to a string, using the operating system's local conventions. The toLocaleString method relies on the underlying operating system in formatting dates. It converts the date to a string using the formatting convention of the operating system where the script is running. For example, in the United States, the month appears before the date (04/15/98), whereas in Germany the date appears before the month (15.04.98). 265 Javascript Syntax Its syntax is as follows: Date.toLocaleString () Return Value Returns the formatted date in a string fromat. Example Try the following example. <html> <head> <title>JavaScript toLocaleString Method</title> </head> <body> <script type="text/javascript"> var dt = new Date(1993, 6, 28, 14, 39, 7); document.write( "Formated Date : " + dt.toLocaleString() ); </script> </body> </html> Output Formated Date : 7/28/1993, 2:39:07 PM toLocaleTimeSring () Javascript date toLocaleTimeString() method converts a date to a string, returning the "date" portion using the current locale's conventions. The toLocaleTimeString method relies on the underlying operating system in formatting dates. It converts the date to a string using the formatting convention of the operating system where the script is running. For example, in the United States, the month appears before the date (04/15/98), whereas in Germany, the date appears before the month (15.04.98). Syntax Its syntax is as follows: 266 Javascript Date.toLocaleTimeString () Return Value Returns the formatted date in a string fromat. Example Try the following example. <html> <head> <title>JavaScript toLocaleTimeString Method</title> </head> <body> <script type="text/javascript"> var dt = new Date(1993, 6, 28, 14, 39, 7); document.write( "Formated Date : " + dt.toLocaleTimeString() ); </script> </body> </html> Output Formated Date : 2:39:07 PM toSource () This method returns a string representing the source code of the object. Note: This method may not be compatible with all the browsers. Syntax The following syntax for toSource () Method. Date.toSource () Return Value  For the built-in Date object, toSource returns Date(...))indicating that the source code is not available a string (new 267 Javascript  For instances of Date, toSource returns a string representing the source code. Example Try the following example. <html> <head> <title>JavaScript toSource Method</title> </head> <body> <script type="text/javascript"> var dt = new Date(1993, 6, 28, 14, 39, 7); document.write( "Formated Date : " + dt.toSource() ); </script> </body> </html> Output Formated Date : (new Date(743850547000)) toString () This method returns a string representing the specified Date object. Syntax The following syntax for toString () Method. Date.toString () Return Value Returns a string representing the specified Date object. Example Try the following example. <html> 268 Javascript <head> <title>JavaScript toString Method</title> </head> <body> <script type="text/javascript"> var dateobject = new Date(1993, 6, 28, 14, 39, 7); stringobj = dateobject.toString(); document.write( "String Object : " + stringobj ); </script> </body> </html> Output String Object : Wed Jul 28 1993 14:39:07 GMT+0530 (India Standard Time) toTimeString () This method returns the time portion of a Date object in human readable form. Syntax Its syntax is as follows: Date.toTimeString () Return Value Returns the time portion of a Date object in human readable form. Example Try the following example. <html> <head> <title>JavaScript toTimeString Method</title> 269 Javascript </head> <body> <script type="text/javascript"> var dateobject = new Date(1993, 6, 28, 14, 39, 7); document.write( dateobject.toTimeString() ); </script> </body> </html> Output 14:39:07 GMT+0530 (India Standard Time) toUTCString () This method converts a date to a string, using the universal time convention. Syntax Its syntax is as follows: Date.toTimeString () Return Value Returns converted date to a string, using the universal time convention. Example Try the following example. <html> <head> <title>JavaScript toUTCString Method</title> </head> <body> <script type="text/javascript"> var dateobject = new Date(1993, 6, 28, 14, 39, 7); document.write( dateobject.toUTCString() ); </script> </body> 270 Javascript </html> Output Wed, 28 Jul 1993 09:09:07 GMT valeOf () This method returns the primitive value of a Date object as a number data type, the number of milliseconds since midnight 01 January, 1970 UTC. Syntax Its syntax is as follows: Date.valueOf () Return Value Returns the primitive value of a Date object. Example Try the following example. <html> <head> <title>JavaScript valueOf Method</title> </head> <body> <script type="text/javascript"> var dateobject = new Date(1993, 6, 28, 14, 39, 7); document.write( dateobject.valueOf() ); </script> </body> </html> 271 Javascript Output 743850547000 Date Static Methods In addition to the many instance methods listed previously, the Date object also defines two static methods. These methods are invoked through the Date() constructor itself. Method Description Date.parse( ) Parses a string representation of a date and time and returns the internal millisecond representation of that date. Date.UTC( ) Returns the millisecond representation of the specified UTC date and time. In the following sections, we will have a few examples to demonstrate the usages of Date Static methods. Date.parse ( ) Javascript date parse() method takes a date string and returns the number of milliseconds since midnight of January 1, 1970. Syntax Its syntax is as follows: Date.parse(datestring) Note: Parameters in the bracket are always optional. Parameter Details datestring: A string representing a date. Return Value Number of milliseconds since midnight of January 1, 1970. Example 272 Javascript Try the following example. <html> <head> <title>JavaScript parse Method</title> </head> <body> <script type="text/javascript"> var msecs = Date.parse( "Aug 28, 2008 23:30:00" ); document.write( "Number of milliseconds from 1970: " + msecs ); </script> </body> </html> Output Number of milliseconds from 1970: 1219946400000 Date.UTC ( ) This method takes a date and returns the number of milliseconds since midnight of January 1, 1970 according to universal time. Syntax Its syntax is as follows: Date.year,month,day,[hours,[minutes,[seconds,[ms]]]) Note: Parameters in the bracket are always optional. Parameter Details     year : A four digit number representing the year. month : An integer between 0 and 11 representing the month. day : An integer between 1 and 31 representing the date. hours : An integer between 0 and 23 representing the hour. 273 Javascript    minutes : An integer between 0 and 59 representing the minutes. seconds : An integer between 0 and 59 representing the seconds. ms : An integer between 0 and 999 representing the milliseconds. Return Value Number of milliseconds since midnight of January 1, 1970. Example Try the following example. <html> <head> <title>JavaScript UTC Method</title> </head> <body> <script type="text/javascript"> var msecs = Date.UTC(2008,9,6); document.write( "Number of milliseconds from 1970: " + msecs ); </script> </body> </html> Output Number of milliseconds from 1970: 1223251200000 274 26. MATH Javascript The math object provides you properties and methods for mathematical constants and functions. Unlike other global objects, Math is not a constructor. All the properties and methods of Math are static and can be called by using Math as an object without creating it. Thus, you refer to the constant pi as Math.PI and you call the sine function as Math.sin(x), where x is the method's argument. Syntax The syntax to call the properties and methods of Math are as follows: var pi_val = Math.PI; var sine_val = Math.sin(30); Math Properties Here is a list of all the properties of Math and their description. Property Description E Euler's constant and the base of natural logarithms, approximately 2.718. LN2 Natural logarithm of 2, approximately 0.693. LN10 Natural logarithm of 10, approximately 2.302. LOG2E Base 2 logarithm of E, approximately 1.442. LOG10E Base 10 logarithm of E, approximately 0.434. PI Ratio of the circumference of a circle to its diameter, approximately 3.14159. SQRT1_2 Square root of 1/2; equivalently, 1 over the square root of 2, approximately 0.707. SQRT2 Square root of 2, approximately 1.414. 275 Javascript In the following sections, we will have a few examples to demonstrate the usage of Math properties. Math-E This is an Euler's constant and the base of natural logarithms, approximately 2.718. Syntax Its syntax is as follows: Math.E Example Try the following example program. <html> <head> <title>JavaScript Math E Property</title> </head> <body> <script type="text/javascript"> var property_value = Math.E document.write("Property Value is :" + property_value); </script> </body> </html> Output Property Value is :2.718281828459045 276 Javascript Math-LN2 It returns the natural logarithm of 2 which is approximately 0.693. Syntax Its syntax is as follows: Math.LN2 Example Try the following example program. <html> <head> <title>JavaScript Math LN2 Property</title> </head> <body> <script type="text/javascript"> var property_value = Math.LN2 document.write("Property Value is : " + property_value); </script> </body> </html> Output Property Value is : 0.6931471805599453 Math-LN10 It returns the natural logarithm of 10 which is approximately 2.302. Syntax Its syntax is as follows: Math.LN10 277 Javascript Example Try the following example program. <html> <head> <title>JavaScript Math LN10 Property</title> </head> <body> <script type="text/javascript"> var property_value = Math.LN10 document.write("Property Value is : " + property_value); </script> </body> </html> Output Property Value is : 2.302585092994046 Math-LOG2E It returns the base 2 logarithm of E which is approximately 1.442. Syntax Its syntax is as follows: Math.LOG2E Example Try the following example program. <html> <head> <title>JavaScript Math LOG2E Property</title> </head> <body> <script type="text/javascript"> 278 Javascript var property_value = Math.LOG2E document.write("Property Value is : " + property_value); </script> </body> </html> Output Property Value is : 1.4426950408889634 Math-LOG10E It returns the base 10 logarithm of E which is approximately 0.434. Syntax Its syntax is as follows: Math.LOG10E Example Try the following example program. <html> <head> <title>JavaScript Math LOG10E Property</title> </head> <body> <script type="text/javascript"> var property_value = Math.LOG10E document.write("Property Value is : " + property_value); </script> </body> </html> Output 279 Javascript Property Value is : 0.4342944819032518 Math-PI It returns the ratio of the circumference of a circle to its diameter which is approximately 3.14159. Syntax Its syntax is as follows: Math.PI Example Try the following example program. <html> <head> <title>JavaScript Math PI Property</title> </head> <body> <script type="text/javascript"> var property_value = Math.PI document.write("Property Value is : " + property_value); </script> </body> </html> Output Property Value is : 3.141592653589793 Math-SQRT1_2 It returns the square root of 1/2; equivalently, 1 over the square root of 2 which is approximately 0.707. 280 Javascript Syntax Its syntax is as follows: Math.SQRT1_2 Example Try the following example program. <html> <head> <title>JavaScript Math SQRT1_2 Property</title> </head> <body> <script type="text/javascript"> var property_value = Math.SQRT1_2 document.write("Property Value is : " + property_value); </script> </body> </html> Output Property Value is : 0.7071067811865476 Math-SQRT2 It returns the square root of 2 which is approximately 1.414. Syntax Its syntax is as follows: Math.SQRT2 Example Try the following example program. <html> 281 Javascript <head> <title>JavaScript Math SQRT2 Property</title> </head> <body> <script type="text/javascript"> var property_value = Math.SQRT2 document.write("Property Value is : " + property_value); </script> </body> </html> Output Property Value is : 1.4142135623730951 Math Methods Here is a list of the methods associated with Math object and their description. Method Description abs() Returns the absolute value of a number. acos() Returns the arccosine (in radians) of a number. asin() Returns the arcsine (in radians) of a number. atan() Returns the arctangent (in radians) of a number. atan2() Returns the arctangent of the quotient of its arguments. ceil() Returns the smallest integer greater than or equal to a number. cos() Returns the cosine of a number. exp() Returns EN, where N is the argument, and E is Euler's constant, the base of the natural logarithm. floor() Returns the largest integer less than or equal to a 282 Javascript number. log() Returns the natural logarithm (base E) of a number. max() Returns the largest of zero or more numbers. min() Returns the smallest of zero or more numbers. pow() Returns base to the exponent power, that is, base exponent. random() Returns a pseudo-random number between 0 and 1. round() Returns the value of a number rounded to the nearest integer. sin() Returns the sine of a number. sqrt() Returns the square root of a number. tan() Returns the tangent of a number. toSource() Returns the string "Math". In the following sections, we will have a few examples to demonstrate the usage of the methods associated with Math. abs () This method returns the absolute value of a number. Syntax Its syntax is as follows: Math.abs( x ) ; Parameter Details x: A number. Return Value Returns the absolute value of a number. Example 283 Javascript Try the following example program. <html> <head> <title>JavaScript Math abs() Method</title> </head> <body> <script type="text/javascript"> var value = Math.abs(-1); document.write("First Test Value : " + value ); var value = Math.abs(null); document.write("<br />Second Test Value : " + value ); var value = Math.abs(20); document.write("<br />Third Test Value : " + value ); var value = Math.abs("string"); document.write("<br />Fourth Test Value : " + value ); </script> </body> </html> Output First Test Value : 1 Second Test Value : 0 Third Test Value : 20 Fourth Test Value : NaN acos () This method returns the arccosine in radians of a number. The acos method returns a numeric value between 0 and pi radians for x between -1 and 1. If the value of number is outside this range, it returns NaN. Syntax 284 Javascript Its syntax is as follows: Math.cos( x ) ; Parameter Details x: A number. Return Value Returns the arccosine in radians of a number. Example Try the following example program. <html> <head> <title>JavaScript Math acos() Method</title> </head> <body> <script type="text/javascript"> var value = Math.acos(-1); document.write("First Test Value : " + value ); var value = Math.acos(null); document.write("<br />Second Test Value : " + value ); var value = Math.acos(30); document.write("<br />Third Test Value : " + value ); var value = Math.acos("string"); document.write("<br />Fourth Test Value : " + value ); </script> </body> </html> Output 285 Javascript First Test Value : 3.141592653589793 Second Test Value : 1.5707963267948966 Third Test Value : NaN Fourth Test Value : NaN asin ( ) This method returns the arcsine in radians of a number. The asin method returns a numeric value between -pi/2 and pi/2 radians for x between -1 and 1. If the value of number is outside this range, it returns NaN. Syntax Its syntax is as follows: Math.asin( x ) ; Parameter Details x: A number. Return Value Returns the arcsine in radians of a number. Example Try the following example program. <html> <head> <title>JavaScript Math asin() Method</title> </head> <body> <script type="text/javascript"> var value = Math.asin(-1); document.write("First Test Value : " + value ); var value = Math.asin(null); document.write("<br />Second Test Value : " + value ); 286 Javascript var value = Math.asin(30); document.write("<br />Third Test Value : " + value ); var value = Math.asin("string"); document.write("<br />Fourth Test Value : " + value ); </script> </body> </html> Output First Test Value : -1.5707963267948966 Second Test Value : 0 Third Test Value : NaN Fourth Test Value : NaN atan ( ) This method returns the arctangent in radians of a number. The atan method returns a numeric value between -pi/2 and pi/2 radians. Syntax Its syntax is as follows: Math.atan( x ) ; Parameter Details x: A number. Return Value Returns the arctangent in radians of a number. Example Try the following example program. <html> <head> 287 Javascript <title>JavaScript Math atan() Method</title> </head> <body> <script type="text/javascript"> var value = Math.atan(-1); document.write("First Test Value : " + value ); var value = Math.atan(.5); document.write("<br />Second Test Value : " + value ); var value = Math.atan(30); document.write("<br />Third Test Value : " + value ); var value = Math.atan("string"); document.write("<br />Fourth Test Value : " + value ); </script> </body> </html> Output First Test Value : -0.7853981633974483 Second Test Value : 0.4636476090008061 Third Test Value : 1.5374753309166493 Fourth Test Value : NaN atan2 ( ) This method returns the arctangent of the quotient of its arguments. The atan2 method returns a numeric value between -pi and pi representing the angle theta of an (x, y) point. Syntax Its syntax is as follows: Math.atan2 ( x, y ) ; 288 Javascript Parameter Details X and y: numbers. Return Value Returns the arctangent in radians of a number. Math.atan2 ( ±0, -0 ) returns ±PI. Math.atan2 ( ±0, +0 ) returns ±0. Math.atan2 ( ±0, -x ) returns ±PI for x < 0. Math.atan2 ( ±0, x ) returns ±0 for x > 0. Math.atan2 ( y, ±0 ) returns -PI/2 for y > 0. Math.atan2 ( ±y, -Infinity ) returns ±PI for finite y > 0. Math.atan2 ( ±y, +Infinity ) returns ±0 for finite y > 0. Math.atan2 ( ±Infinity, +x ) returns ±PI/2 for finite x. Math.atan2 ( ±Infinity, -Infinity ) returns ±3*PI/4. Math.atan2 ( ±Infinity, +Infinity ) returns ±PI/4. Example Try the following example program. <html> <head> <title>JavaScript Math atan2() Method</title> </head> <body> <script type="text/javascript"> var value = Math.atan2(90,15); document.write("First Test Value : " + value ); var value = Math.atan2(15,90); document.write("<br />Second Test Value : " + value ); var value = Math.atan2(0, -0); document.write("<br />Third Test Value : " + value ); 289 Javascript var value = Math.atan2(+Infinity, -Infinity); document.write("<br />Fourth Test Value : " + value ); </script> </body> </html> Output First Test Value : 1.4056476493802699 Second Test Value : 0.16514867741462683 Third Test Value : 3.141592653589793 Fourth Test Value : 2.356194490192345 ceil ( ) This method returns the smallest integer greater than or equal to a number. Syntax Its syntax is as follows: Math.ceil ( x ) ; Parameter Details x: a number. Return Value Returns the smallest integer greater than or equal to a number. Example Try the following example program. <html> <head> <title>JavaScript Math ceil() Method</title> </head> <body> <script type="text/javascript"> 290 Javascript var value = Math.ceil(45.95); document.write("First Test Value : " + value ); var value = Math.ceil(45.20); document.write("<br />Second Test Value : " + value ); var value = Math.ceil(-45.95); document.write("<br />Third Test Value : " + value ); var value = Math.ceil(-45.20); document.write("<br />Fourth Test Value : " + value ); </script> </body> </html> Output First Test Value : 46 Second Test Value : 46 Third Test Value : -45 Fourth Test Value : -45 cos ( ) This method returns the cosine of a number. The cos method returns a numeric value between -1 and 1, which represents the cosine of the angle. Syntax Its syntax is as follows: Math.cos ( x ) ; Parameter Details x: a number. Return Value Returns the cosine of a number. 291 Javascript Example Try the following example program. <html> <head> <title>JavaScript Math cos() Method</title> </head> <body> <script type="text/javascript"> var value = Math.cos(90); document.write("First Test Value : " + value ); var value = Math.cos(30); document.write("<br />Second Test Value : " + value ); var value = Math.cos(-1); document.write("<br />Third Test Value : " + value ); var value = Math.cos(2*Math.PI); document.write("<br />Fourth Test Value : " + value ); </script> </body> </html> Output First Test Value : -0.4480736161291702 Second Test Value : 0.15425144988758405 Third Test Value : 0.5403023058681398 Fourth Test Value : 1 exp ( ) This method returns Ex, where x is the argument, and E is the Euler's constant, the base of the natural logarithms. 292 Javascript Syntax Its syntax is as follows: Math.exp ( x ) ; Parameter Details x: a number. Return Value Returns the exponential value of the variable x. Example Try the following example program. <html> <head> <title>JavaScript Math exp() Method</title> </head> <body> <script type="text/javascript"> var value = Math.exp(1); document.write("First Test Value : " + value ); var value = Math.exp(30); document.write("<br />Second Test Value : " + value ); var value = Math.exp(-1); document.write("<br />Third Test Value : " + value ); var value = Math.exp(.5); document.write("<br />Fourth Test Value : " + value ); </script> </body> </html> 293 Javascript Output First Test Value : 2.718281828459045 Second Test Value : 10686474581524.482 Third Test Value : 0.3678794411714424 Fourth Test Value : 1.6487212707001282 floor ( ) This method returns the largest integer less than or equal to a number. Syntax Its syntax is as follows: Math.floor ( x ) ; Parameter Details x: a number. Return Value Returns the largest integer less than or equal to a number x. Example Try the following example program. <html> <head> <title>JavaScript Math floor() Method</title> </head> <body> <script type="text/javascript"> var value = Math.floor(10.3); document.write("First Test Value : " + value ); var value = Math.floor(30.9); document.write("<br />Second Test Value : " + value ); var value = Math.floor(-2.9); 294 Javascript document.write("<br />Third Test Value : " + value ); var value = Math.floor(-2.2); document.write("<br />Fourth Test Value : " + value ); </script> </body> </html> Output First Test Value : 10 Second Test Value : 30 Third Test Value : -3 Fourth Test Value : -3 log ( ) This method returns the natural logarithm (base E) of a number. If the value of number is negative, the return value is always NaN. Syntax Its syntax is as follows: Math.log ( x ) ; Parameter Details x: a number. Return Value Returns the natural logarithm (base E) of a number. Example Try the following example program. <html> <head> <title>JavaScript Math log() Method</title> </head> <body> 295 Javascript <script type="text/javascript"> var value = Math.log(10); document.write("First Test Value : " + value ); var value = Math.log(0); document.write("<br />Second Test Value : " + value ); var value = Math.log(-1); document.write("<br />Third Test Value : " + value ); var value = Math.log(100); document.write("<br />Fourth Test Value : " + value ); </script> </body> </html> Output First Test Value : 2.302585092994046 Second Test Value : -Infinity Third Test Value : NaN Fourth Test Value : 4.605170185988092 max ( ) This method returns the largest of zero or more numbers. If no arguments are given, the results is –Infinity. Syntax Its syntax is as follows: Math.max(value1, value2, ... valueN ) ; Parameter Details value1, value2, ... valueN : Numbers. Return Value 296 Javascript Returns the largest of zero or more numbers. Example Try the following example program. <html> <head> <title>JavaScript Math max() Method</title> </head> <body> <script type="text/javascript"> var value = Math.max(10, 20, -1, 100); document.write("First Test Value : " + value ); var value = Math.max(-1, -3, -40); document.write("<br />Second Test Value : " + value ); var value = Math.max(0, -1); document.write("<br />Third Test Value : " + value ); var value = Math.max(100); document.write("<br />Fourth Test Value : " + value ); </script> </body> </html> Output First Test Value : 100 Second Test Value : -1 Third Test Value : 0 Fourth Test Value : 100 297 Javascript min ( ) This method returns the smallest of zero or more numbers. If no arguments are given, the results is +Infinity. Syntax Its syntax is as follows: Math.min (value1, value2, ... valueN ) ; Parameter Details value1, value2, ... valueN : Numbers. Return Value Returns the smallest of zero or more numbers. Example Try the following example program. <html> <head> <title>JavaScript Math min() Method</title> </head> <body> <script type="text/javascript"> var value = Math.min(10, 20, -1, 100); document.write("First Test Value : " + value ); var value = Math.min(-1, -3, -40); document.write("<br />Second Test Value : " + value ); var value = Math.min(0, -1); document.write("<br />Third Test Value : " + value ); var value = Math.min(100); document.write("<br />Fourth Test Value : " + value ); 298 Javascript </script> </body> </html> Output First Test Value : -1 Second Test Value : -40 Third Test Value : -1 Fourth Test Value : 100 pow ( ) This method returns the base to the exponent power, that is, baseexponent. Syntax Its syntax is as follows: Math.pow(base, exponent ); Parameter Details   base : The base number. exponents : The exponent to which to raise the base. Return Value Returns the base to the exponent power, that is, baseexponent. Example Try the following example program. <html> <head> <title>JavaScript Math pow() Method</title> </head> <body> <script type="text/javascript"> 299 Javascript var value = Math.pow(7, 2); document.write("First Test Value : " + value ); var value = Math.pow(8, 8); document.write("<br />Second Test Value : " + value ); var value = Math.pow(-1, 2); document.write("<br />Third Test Value : " + value ); var value = Math.pow(0, 10); document.write("<br />Fourth Test Value : " + value ); </script> </body> </html> Output First Test Value : 49 Second Test Value : 16777216 Third Test Value : 1 Fourth Test Value : 0 random ( ) This method returns a random number between 0 (inclusive) and 1 (exclusive). Syntax Its syntax is as follows: Math.random ( ); Return Value Returns a random number between 0 (inclusive) and 1 (exclusive). Example Try the following example program. 300 Javascript <html> <head> <title>JavaScript Math random() Method</title> </head> <body> <script type="text/javascript"> var value = Math.random( ); document.write("First Test Value : " + value ); var value = Math.random( ); document.write("<br />Second Test Value : " + value ); var value = Math.random( ); document.write("<br />Third Test Value : " + value ); var value = Math.random( ); document.write("<br />Fourth Test Value : " + value ); </script> </body> </html> Output First Test Value : 0.4093269258737564 Second Test Value : 0.023646741174161434 Third Test Value : 0.2672571325674653 Fourth Test Value : 0.38755513448268175 round ( ) This method returns the value of a number rounded to the nearest integer. Syntax Its syntax is as follows: Math.round ( ); 301 Javascript Return Value Returns the value of a number rounded to the nearest integer. Example Try the following example program. <html> <head> <title>JavaScript Math round() Method</title> </head> <body> <script type="text/javascript"> var value = Math.round( 0.5 ); document.write("First Test Value : " + value ); var value = Math.round( 20.7 ); document.write("<br />Second Test Value : " + value ); var value = Math.round( 20.3 ); document.write("<br />Third Test Value : " + value ); var value = Math.round( -20.3 ); document.write("<br />Fourth Test Value : " + value ); </script> </body> </html> Output First Test Value : 1 Second Test Value : 21 Third Test Value : 20 Fourth Test Value : -20 302 Javascript sin ( ) This method returns the sine of a number. The sin method returns a numeric value between -1 and 1, which represents the sine of the argument. Syntax Its syntax is as follows: Math.sin ( x ); Parameter Details x: A number. Return Value Returns the sine of a number. Example Try the following example program. <html> <head> <title>JavaScript Math sin() Method</title> </head> <body> <script type="text/javascript"> var value = Math.sin( 0.5 ); document.write("First Test Value : " + value ); var value = Math.sin( 90 ); document.write("<br />Second Test Value : " + value ); var value = Math.sin( 1 ); document.write("<br />Third Test Value : " + value ); var value = Math.sin( Math.PI/2 ); document.write("<br />Fourth Test Value : " + value ); 303 Javascript </script> </body> </html> Output First Test Value : 0.479425538604203 Second Test Value : 0.8939966636005579 Third Test Value : 0.8414709848078965 Fourth Test Value : 1 sqrt ( ) This method returns the square root of a number. If the value of a number is negative, sqrt returns NaN. Syntax Its syntax is as follows: Math.sqrt ( x ); Parameter Details x: A number. Return Value Returns the square root of a given number. Example Try the following example program. <html> <head> <title>JavaScript Math sqrt() Method</title> </head> <body> <script type="text/javascript"> 304 Javascript var value = Math.sqrt( 0.5 ); document.write("First Test Value : " + value ); var value = Math.sqrt( 81 ); document.write("<br />Second Test Value : " + value ); var value = Math.sqrt( 13 ); document.write("<br />Third Test Value : " + value ); var value = Math.sqrt( -4 ); document.write("<br />Fourth Test Value : " + value ); </script> </body> </html> Output First Test Value : 0.7071067811865476 Second Test Value : 9 Third Test Value : 3.605551275463989 Fourth Test Value : NaN tan ( ) This method returns the tangent of a number. The tan method returns a numeric value that represents the tangent of the angle. Syntax Its syntax is as follows: Math.tan ( x ); Parameter Details x: A number representing an angle in radians. Return Value Returns the tangent of a number. 305 Javascript Example Try the following example program. <html> <head> <title>JavaScript Math tan() Method</title> </head> <body> <script type="text/javascript"> var value = Math.tan( -30 ); document.write("First Test Value : " + value ); var value = Math.tan( 90 ); document.write("<br />Second Test Value : " + value ); var value = Math.tan( 45 ); document.write("<br />Third Test Value : " + value ); var value = Math.tan( Math.PI/180 ); document.write("<br />Fourth Test Value : " + value ); </script> </body> </html> Output First Test Value : 1 Second Test Value : 21 Third Test Value : 20 Fourth Test Value : -20 toSource ( ) This method returns the string "Math". But this method does not work with IE. 306 Javascript Syntax Its syntax is as follows: Math.toSource ( ); Return Value Returns the string “Math”. Example Try the following example program. <html> <head> <title>JavaScript Math toSource() Method</title> </head> <body> <script type="text/javascript"> var value = Math.toSource( ); document.write("Value : " + value ); </script> </body> </html> Output Value : Math 307 27. REGEXP Javascript A regular expression is an object that describes a pattern of characters. The JavaScript RegExp class represents regular expressions, and both String and RegExp define methods that use regular expressions to perform powerful pattern-matching and search-and-replace functions on text. Syntax A regular expression could be defined with the RegExp() constructor, as follows: var pattern = new RegExp(pattern, attributes); or simply var pattern = /pattern/attributes; Here is the description of the parameters:   pattern: A string that specifies the pattern of the regular expression or another regular expression. attributes: An optional string containing any of the "g", "i", and "m" attributes that specify global, case-insensitive, and multiline matches, respectively. Brackets Brackets ([]) have a special meaning when used in the context of regular expressions. They are used to find a range of characters. Expression Description [...] Any one character between the brackets. [^...] Any one character not between the brackets. [0-9] It matches any decimal digit from 0 through 9. 308 Javascript [a-z] It matches any lowercase z. [A-Z] It matches any character from uppercase uppercase Z. A through [a-Z] It matches any uppercase Z. a character character from from lowercase lowercase a through through The ranges shown above are general; you could also use the range [0-3] to match any decimal digit ranging from 0 through 3, or the range [b-v] to match any lowercase character ranging from b through v. Quantifiers The frequency or position of bracketed character sequences and single characters can be denoted by a special character. Each special character has a specific connotation. The +, *, ?, and $ flags all follow a character sequence. Expression Description p+ It matches any string containing at least one p. p* It matches any string containing zero or more p's. p? It matches any string containing one or more p's. p{N} It matches any string containing a sequence of N p's p{2,3} It matches any string containing a sequence of two or three p's. p{2, } It matches any string containing a sequence of at least two p's. p$ It matches any string with p at the end of it. ^p It matches any string with p at the beginning of it. 309 Javascript Examples Following examples explain more about matching characters. Expression Description [^a-zA-Z] It matches any string not containing any of the characters ranging from a through z and A through Z. p.p ^.{2}$ <b>(.*)</b> p(hp)* It matches any string containing p, character, in turn followed by another p. followed by any It matches any string containing exactly two characters. It matches any string enclosed within <b> and </b>. It matches any string containing a p followed by zero or more instances of the sequence hp. Literal Characters Character Description Alphanumeric Itself \0 The NUL character (\u0000) \t Tab (\u0009) \n Newline (\u000A) \v Vertical tab (\u000B) \f Form feed (\u000C) \r Carriage return (\u000D) \xnn The Latin character specified by the hexadecimal number nn; for example, \x0A is the same as \n \uxxxx The Unicode character specified by the hexadecimal number xxxx; for example, \u0009 is the same as \t 310 Javascript \cX The control character ^X; for example, \cJ is equivalent to the newline character \n Metacharacters A metacharacter is simply an alphabetical character preceded by a backslash that acts to give the combination a special meaning. For instance, you can search for a large sum of money using the '\d' metacharacter: /([\d]+)000/. Here \d will search for any string of numerical character. The following table lists a set of metacharacters which can be used in PERL Style Regular Expressions. Character Description . a single character \s a whitespace character (space, tab, newline) \S non-whitespace character \d a digit (0-9) \D a non-digit \w a word character (a-z, A-Z, 0-9, _) \W a non-word character [\b] a literal backspace (special case). [aeiou] matches a single character in the given set [^aeiou] matches a single character outside the given set (foo|bar|baz) matches any of the alternatives specified Modifiers Several modifiers are available that can simplify the way you work with regexps, like case sensitivity, searching in multiple lines, etc. Modifier i Description Performs case-insensitive matching. 311 Javascript m Specifies that if the string has newline or carriage return characters, the ^ and $ operators will now match against a newline boundary, instead of a string boundary g Performs a global matchthat is, find all matches rather than stopping after the first match. RegExp Properties Here is a list of the properties associated with RegExp and their description. Property Description constructor Specifies the prototype. global Specifies if the "g" modifier is set. ignoreCase Specifies if the "i" modifier is set. lastIndex The index at which to start the next match. multiline Specifies if the "m" modifier is set. source The text of the pattern. function that creates an object's In the following sections, we will have a few examples to demonstrate the usage of RegExp properties. constructor It returns a reference to the array function that created the instance's prototype. Syntax Its syntax is as follows: RegExp.constructor Return Value Returns the function that created this object's instance. 312 Javascript Example Try the following example program. <html> <head> <title>JavaScript RegExp constructor Property</title> </head> <body> <script type="text/javascript"> var re = new RegExp( "string" ); document.write("re.constructor is:" + re.constructor); </script> </body> </html> Output re.constructor is:function RegExp() { [native code] global global is a read-only boolean property of RegExp objects. It specifies whether a particular regular expression performs global matching, i.e., whether it was created with the "g" attribute. Syntax Its syntax is as follows: RegExpObject.global Return Value Returns "TRUE" if the "g" modifier is set, "FALSE" otherwise. Example 313 Javascript Try the following example program. <html> <head> <title>JavaScript RegExp global Property</title> </head> <body> <script type="text/javascript"> var re = new RegExp( "string" ); if ( re.global ){ document.write("Test1 - Global property is set"); }else{ document.write("Test1 - Global property is not set"); } re = new RegExp( "string", "g" ); if ( re.global ){ document.write("<br />Test2 - Global property is set"); }else{ document.write("<br />Test2 - Global property is not set"); } </script> </body> </html> Output Test1 - Global property is not set Test2 - Global property is set ignoreCase ignoreCase is a read-only boolean property of RegExp objects. It specifies whether a particular regular expression performs case-insensitive matching, i.e., whether it was created with the "i" attribute. 314 Javascript Syntax Its syntax is as follows: RegExpObject.ignoreCase Return Value Returns "TRUE" if the "i" modifier is set, "FALSE" otherwise. Example Try the following example program. <html> <head> <title>JavaScript RegExp ignoreCase Property</title> </head> <body> <script type="text/javascript"> var re = new RegExp( "string" ); if ( re.ignoreCase ){ document.write("Test1 - ignoreCase property is set"); }else{ document.write("Test1 - ignoreCase property is not set"); } re = new RegExp( "string", "i" ); if ( re.ignoreCase ){ document.write("<br />Test2 - ignoreCase property is set"); }else{ document.write("<br />Test2 - ignoreCase property is not set"); } </script> </body> </html> Output 315 Javascript Test1 - ignoreCase property is not set Test2 - ignoreCase property is set lastIndex lastIndex is a read/write property of RegExp objects. For regular expressions with the "g" attribute set, it contains an integer that specifies the character position immediately following the last match found by the RegExp.exec() and RegExp.test() methods. These methods use this property as the starting point for the next search they conduct. This property allows you to call those methods repeatedly, to loop through all matches in a string and works only if the "g" modifier is set. This property is read/write, so you can set it at any time to specify where in the target string, the next search should begin. exec() and test() automatically reset the lastIndex to 0 when they fail to find a match (or another match). Syntax Its syntax is as follows: RegExpObject.lastIndex Return Value Returns an integer that specifies the character position immediately following the last match. Example Try the following example program. <html> <head> <title>JavaScript RegExp lastIndex Property</title> </head> <body> <script type="text/javascript"> var str = "Javascript is an interesting scripting language"; var re = new RegExp( "script", "g" ); re.test(str); 316 Javascript document.write("Test 1 - Current Index: " + re.lastIndex); re.test(str); document.write("<br />Test 2 - Current Index: " + re.lastIndex); </script> </body> </html> Output Test 1 - Current Index: 10 Test 2 - Current Index: 35 multiline multiline is a read-only boolean property of RegExp objects. It specifies whether a particular regular expression performs multiline matching, i.e., whether it was created with the "m" attribute. Syntax Its syntax is as follows: RegExpObject.multiline Return Value Returns "TRUE" if the "m" modifier is set, "FALSE" otherwise. Example Try the following example program. <html> <head> <title>JavaScript RegExp multiline Property</title> </head> <body> <script type="text/javascript"> var re = new RegExp( "string" ); 317 Javascript if ( re.multiline ){ document.write("Test1-multiline property is set"); }else{ document.write("Test1-multiline property is not set"); } re = new RegExp( "string", "m" ); if ( re.multiline ){ document.write("<br/>Test2-multiline property is set"); }else{ document.write("<br/>Test2-multiline property is not set"); } </script> </body> </html> Output Test1-multiline property is not set Test2-multiline property is set source source is a read-only string property of RegExp objects. It contains the text of the RegExp pattern. This text does not include the delimiting slashes used in regular-expression literals, and it does not include the "g", "i", and "m" attributes. Syntax Its syntax is as follows: RegExpObject.source Return Value Returns the text used for pattern matching. Example 318 Javascript Try the following example program. <html> <head> <title>JavaScript RegExp source Property</title> </head> <body> <script type="text/javascript"> var str = "Javascript is an interesting scripting language"; var re = new RegExp( "script", "g" ); re.test(str); document.write("The regular expression is : " + re.source); </script> </body> </html> Output The regular expression is : script RegExp Methods Here is a list of the methods associated with RegExp along with their description. Method Description exec() Executes a search for a match in its string parameter. test() Tests for a match in its string parameter. toSource() Returns an object literal representing the specified object; you can use this value to create a new object. toString() Returns a string representing the specified object. In the following sections, we will have a few examples to demonstrate the usage of RegExp methods. 319 Javascript exec ( ) The exec method searches string for text that matches regexp. If it finds a match, it returns an array of results; otherwise, it returns null. Syntax Its syntax is as follows: RegExpObject.exec( string ); Parameter Details string: The string to be searched. Return Value Returns the matched text if a match is found, and null if not. Example Try the following example program. <html> <head> <title>JavaScript RegExp exec Method</title> </head> <body> <script type="text/javascript"> var str = "Javascript is an interesting scripting language"; var re = new RegExp( "script", "g" ); var result = re.exec(str); document.write("Test 1 - returned value : " + result); re = new RegExp( "pushing", "g" ); var result = re.exec(str); document.write("<br />Test 2 - returned value : " + result); </script> </body> </html> 320 Javascript Output Test 1 - returned value : script Test 2 - returned value : null test ( ) The test method searches string for text that matches regexp. If it finds a match, it returns true; otherwise, it returns false. Syntax Its syntax is as follows: RegExpObject.test( string ); Parameter Details string: The string to be searched. Return Value Returns the matched text if a match is found, and null if not. Example Try the following example program. <html> <head> <title>JavaScript RegExp test Method</title> </head> <body> <script type="text/javascript"> var str = "Javascript is an interesting scripting language"; var re = new RegExp( "script", "g" ); var result = re.test(str); document.write("Test 1 - returned value : " + result); re = new RegExp( "pushing", "g" ); var result = re.test(str); 321 Javascript document.write("<br />Test 2 - returned value : " + result); </script> </body> </html> Output Test 1 - returned value : true Test 2 - returned value : false toSource ( ) The toSource method string represents the source code of the object. This method does not work with all the browsers. Syntax Its syntax is as follows: RegExpObject.toSource ( string ); Return Value Returns the string representing the source code of the object. Example Try the following example program. <html> <head> <title>JavaScript RegExp toSource Method</title> </head> <body> <script type="text/javascript"> var str = "Javascript is an interesting scripting language"; var re = new RegExp( "script", "g" ); var result = re.toSource(str); document.write("Test 1 - returned value : " + result); 322 Javascript re = new RegExp( "/", "g" ); var result = re.toSource(str); document.write("<br />Test 2 - returned value : " + result); </script> </body> </html> Output Test 1 - returned value : /script/g Test 2 - returned value : /\//g toString ( ) The toString method returns a string representation of a regular expression in the form of a regular-expression literal. Syntax Its syntax is as follows: RegExpObject.toString ( ); Return Value Returns the string representing of a regular expression. Example Try the following example program. <html> <head> <title>JavaScript RegExp toString Method</title> </head> <body> <script type="text/javascript"> var str = "Javascript is an interesting scripting language"; var re = new RegExp( "script", "g" ); var result = re.toString(str); 323 Javascript document.write("Test 1 - returned value : " + result); re = new RegExp( "/", "g" ); var result = re.toString(str); document.write("<br />Test 2 - returned value : " + result); </script> </body> </html> Output Test 1 - returned value : /script/g Test 2 - returned value : /\//g 324 28. DOM Javascript Every web page resides inside a browser window which can be considered as an object. A Document object represents the HTML document that is displayed in that window. The Document object has various properties that refer to other objects which allow access to and modification of document content. The way a document content is accessed and modified is called the Document Object Model, or DOM. The Objects are organized in a hierarchy. This hierarchical structure applies to the organization of objects in a Web document.     Window object: Top of the hierarchy. It is the outmost element of the object hierarchy. Document object: Each HTML document that gets loaded into a window becomes a document object. The document contains the contents of the page. Form object: Everything enclosed in the <form>...</form> tags sets the form object. Form control elements: The form object contains all the elements defined for that object such as text fields, buttons, radio buttons, and checkboxes. Here is a simple hierarchy of a few important objects: 325 Javascript There are several DOMs in existence. The following sections explain each of these DOMs in detail and describe how you can use them to access and modify document content.    The Legacy DOM: This is the model which was introduced in early versions of JavaScript language. It is well supported by all browsers, but allows access only to certain key portions of documents, such as forms, form elements, and images. The W3C DOM: This document object model allows access and modification of all document content and is standardized by the World Wide Web Consortium (W3C). This model is supported by almost all the modern browsers. The IE4 DOM: This document object model was introduced in Version 4 of Microsoft's Internet Explorer browser. IE 5 and later versions include support for most basic W3C DOM features. The Legacy DOM This is the model which was introduced in early versions of JavaScript language. It is well supported by all browsers, but allows access only to certain key portions of documents, such as forms, form elements, and images. This model provides several read-only properties, such as title, URL, and lastModified provide information about the document as a whole. Apart from that, there are various methods provided by this model which can be used to set and get document property values. Document Properties in Legacy DOM Here is a list of the document properties which can be accessed using Legacy DOM. S.No Property and Description alinkColor 1 Deprecated - A string that specifies the color of activated links. Ex: document.alinkColor anchors[ ] 2 An array of Anchor objects, one for each anchor that appears in the document 326 Javascript Ex: document.anchors[0], document.anchors[1] and so on applets[ ] 3 An array of Applet objects, one for each applet that appears in the document Ex: document.applets[0], document.applets[1] and so on bgColor 4 Deprecated - A string that specifies the background color of the document. Ex: document.bgColor Cookie 5 A string valued property with special behavior that allows the cookies associated with this document to be queried and set. Ex: document.cookie Domain 6 A string that specifies the Internet domain the document is from. Used for security purpose. Ex: document.domain embeds[ ] 7 An array of objects that represent data embedded in the document with the <embed> tag. A synonym for plugins []. Some plugins and ActiveX controls can be controlled with JavaScript code. Ex: document.embeds[0], document.embeds[1] and so on fgColor 8 A string that specifies the default text color for the document Ex: document.fgColor 327 Javascript forms[ ] 9 An array of Form objects, one for each HTML form that appears in the document. Ex: document.forms[0], document.forms[1] and so on images[ ] 10 An array of Image objects, one for each image that is embedded in the document with the HTML <img> tag. Ex: document.images[0], document.images[1] and so on lastModified 11 A read-only string that specifies the date of the most recent change to the document Ex: document.lastModified linkColor 12 Deprecated - A string that specifies the color of unvisited links Ex: document.linkColor links[ ] 13 It is a document link array. Ex: document.links[0], document.links[1] and so on Location 14 The URL of the document. Deprecated in favor of the URL property. Ex: document.location plugins[ ] 15 A synonym for the embeds[ ] 328 Javascript Ex: document.plugins[0], document.plugins[1] and so on Referrer 16 A read-only string that contains the URL of the document, if any, from which the current document was linked. Ex: document.referrer Title 17 The text contents of the <title> tag. Ex: document.title URL 18 A read-only string that specifies the URL of the document. Ex: document.URL vlinkColor 19 Deprecated - A string that specifies the color of visited links. Ex: document.vlinkColor Document Methods in Legacy DOM Here is a list of methods supported by Legacy DOM. S.No Property and Description clear( ) 1 Deprecated - Erases the contents of the document and returns nothing. Ex: document.clear( ) close( ) 2 Closes a document stream opened with the open( ) method and returns nothing. 329 Javascript Ex: document.close( ) open( ) 3 Deletes existing document content and opens a stream to which new document contents may be written. Returns nothing. Ex: document.open( ) write( value, ...) 4 Inserts the specified string or strings into the document currently being parsed or appends to document opened with open( ). Returns nothing. Ex: document.write( value, ...) writeln( value, ...) 5 Identical to write( ), except that it appends a newline character to the output. Returns nothing. Ex: document.writeln( value, ...) Example We can locate any HTML element within any HTML document using HTML DOM. For instance, if a web document contains a form element, then using JavaScript, we can refer to it as document.forms[0]. If your Web document includes two form elements, the first form is referred to as document.forms[0] and the second as document.forms[1]. Using the hierarchy and properties given above, we can access the first form element using document.forms[0].elements[0] and so on. Here is an example to access document properties using Legacy DOM method. <html> <head> <title> Document Title </title> <script type="text/javascript"> <!-function myFunc() 330 Javascript { var ret = document.title; alert("Document Title : " + ret ); var ret = document.URL; alert("Document URL : " + ret ); var ret = document.forms[0]; alert("Document First Form : " + ret ); var ret = document.forms[0].elements[1]; alert("Second element : " + ret ); } //--> </script> </head> <body> <h1 id="title">This is main title</h1> <p>Click the following to see the result:</p> <form name="FirstForm"> <input type="button" value="Click Me" onclick="myFunc();" /> <input type="button" value="Cancel"> </form> <form name="SecondForm"> <input type="button" value="Don't ClickMe"/> </form> </body> </html> Output 331 Javascript This is main title Click the following to see the result: Click Me Cancel Don’t Click Me NOTE: This example returns objects for forms and elements and we would have to access their values by using those object properties which are not discussed in this tutorial. The W3C DOM This document object model allows access and modification of all document content and is standardized by the World Wide Web Consortium (W3C). This model is supported by almost all the modern browsers. The W3C DOM standardizes most of the features of the legacy DOM and adds new ones as well. In addition to supporting forms[ ], images[ ], and other array properties of the Document object, it defines methods that allow scripts to access and manipulate any document element and not just special-purpose elements like forms and images. Document Properties in W3C DOM This model supports all the properties available in Legacy DOM. Additionally, here is a list of document properties which can be accessed using W3C DOM. S.No Property and Description Body 1 A reference to the Element object that represents the <body> tag of this document. Ex: document.body defaultView 2 It is a read-only property and represents the window in which the document is displayed. 332 Javascript Ex: document.defaultView documentElement 3 A read-only reference to the <html> tag of the document. Ex: document.documentElement8/31/2008 Implementation 4 It is a read-only property and represents the DOMImplementation object that represents the implementation that created this document. Ex: document.implementation Document Methods in W3C DOM This model supports all the methods available in Legacy DOM. Additionally, here is a list of methods supported by W3C DOM. S.No Property and Description createAttribute( name) 1 Returns a newly-created Attr node with the specified name. Ex: document.createAttribute( name) createComment( text) 2 Creates and returns a new Comment node containing the specified text. Ex: document.createComment( text) createDocumentFragment( ) 3 Creates and returns an empty DocumentFragment node. Ex: document.createDocumentFragment( ) 333 Javascript createElement( tagName) 4 Creates and returns a new Element node with the specified tag name. Ex: document.createElement( tagName) createTextNode( text) 5 Creates and returns a new Text node that contains the specified text. Ex: document.createTextNode( text) getElementById( id) 6 Returns the Element of this document that has the specified value for its id attribute, or null if no such Element exists in the document. Ex: document.getElementById( id) getElementsByName( name) 7 Returns an array of nodes of all elements in the document that have a specified value for their name attribute. If no such elements are found, returns a zero-length array. Ex: document.getElementsByName( name) getElementsByTagName( tagname) 8 Returns an array of all Element nodes in this document that have the specified tag name. The Element nodes appear in the returned array in the same order they appear in the document source. Ex: document.getElementsByTagName( tagname) importNode( importedNode, deep) 9 Creates and returns a copy of a node from some other document that is suitable for insertion into this document. If the deep argument is true, it recursively copies the children of the node too. Supported in DOM Version 2 334 Javascript Ex: document.importNode( importedNode, deep) Example This is very easy to manipulate ( Accessing and Setting ) document element using W3C DOM. You can use any of the methods like getElementById, getElementsByName, or getElementsByTagName. Here is an example to access document properties using W3C DOM method. <html> <head> <title> Document Title </title> <script type="text/javascript"> <!-function myFunc() { var ret = document.getElementsByTagName("title"); alert("Document Title : " + ret[0].text ); var ret = document.getElementById("heading"); alert("Document URL : " + ret.innerHTML ); } //--> </script> </head> <body> <h1 id="heading">This is main title</h1> <p>Click the following to see the result:</p> <form id="form1" name="FirstForm"> <input type="button" value="Click Me" onclick="myFunc();" /> <input type="button" value="Cancel"> </form> <form d="form2" name="SecondForm"> 335 Javascript <input type="button" value="Don't ClickMe"/> </form> </body> </html> NOTE: This example returns objects for forms and elements and we would have to access their values by using those object properties which are not discussed in this tutorial. Output This is main title Click the following to see the result: Click Me Cancel Don’t Click Me The IE 4 DOM This document object model was introduced in Version 4 of Microsoft's Internet Explorer browser. IE 5 and later versions include support for most basic W3C DOM features. Document Properties in IE 4 DOM The following non-standard (and non-portable) properties are defined by Internet Explorer 4 and later versions. S.No Property and Description activeElement 1 A read-only property that refers to the input element that is currently active (i.e., has the input focus). Ex: document.activeElement 336 Javascript all[ ] 2 An array of all Element objects within the document. This array may be indexed numerically to access elements in source order, or it may be indexed by element id or name. Ex: document.all[ ] Charset 3 The character set of the document. Ex: document.charset children[ ] 4 An array that contains the HTML elements that are the direct children of the document. Note that this is different from the all [ ] array that contains all the elements in the document, regardless of their position in the containment hierarchy. Ex: document.children[ ] defaultCharset 5 The default character set of the document. Ex: document.defaultCharset expand 6 This property, if set to false, prevents client-side objects from being expanded. Ex: document.expando parentWindow 7 The window that contains the document. Ex: document.parentWindow 8 readyState 337 Javascript Specifies the loading status of a document. It has one of the following four string values: Ex: document.readyState Uninitialized 9 The document has not started loading. Example: document.uninitialized Loading 10 The document is loading. Ex: document.loading interactive 11 The document has loaded sufficiently for the user to interact with it. Ex: document.interactive complete 12 The document is completely loaded. Ex: document.complete Document Methods in IE4 DOM This model supports all the methods available in Legacy DOM. Additionally, here is a list of methods supported by IE4 DOM. S.No Property and Description elementFromPoint(x,y) 1 Returns the Element located at a specified point. Ex: document.elementFromPoint(x,y) 338 Javascript Example The IE 4 DOM does not support the getElementById() method. Instead, it allows you to look up arbitrary document elements by id attribute within the all [] array of the document object. Here's how to find all <li> tags within the first <ul> tag. Note that you must specify the desired HTML tag name in uppercase with the all.tags() method. var lists = document.all.tags("UL"); var items = lists[0].all.tags("LI"); Here is another example to access document properties using IE4 DOM method. <html> <head> <title> Document Title </title> <script type="text/javascript"> <!-function myFunc() { var ret = document.all["heading"]; alert("Document Heading : " + ret.innerHTML ); var ret = document.all.tags("P");; alert("First Paragraph : " + ret[0].innerHTML); } //--> </script> </head> <body> <h1 id="heading">This is main title</h1> <p>Click the following to see the result:</p> <form id="form1" name="FirstForm"> <input type="button" value="Click Me" onclick="myFunc();" /> <input type="button" value="Cancel"> 339 Javascript </form> <form d="form2" name="SecondForm"> <input type="button" value="Don't ClickMe"/> </form> </body> </html> NOTE: This example returns objects for forms and elements and we would have to access their values by using those object properties which are not discussed in this tutorial. Output This is main title Click the following to see the result: Click Me Cancel Don’t Click Me DOM Compatibility If you want to write a script with the flexibility to use either W3C DOM or IE 4 DOM depending on their availability, then you can use a capability-testing approach that first checks for the existence of a method or property to determine whether the browser has the capability you desire. For example: if (document.getElementById) { // If the W3C method exists, use it } else if (document.all) { // If the all[] array exists, use it } else { 340 Javascript // Otherwise use the legacy DOM } 341 Javascript Part 3: JavaScript Advanced 342 29. Javascript ERRORS AND EXCEPTIONS There are three types of errors in programming: (a) Syntax Errors, (b) Runtime Errors, and (c) Logical Errors. Syntax Errors Syntax errors, also called parsing errors, occur at compile time in traditional programming languages and at interpret time in JavaScript. For example, the following line causes a syntax error because it is missing a closing parenthesis. <script type="text/javascript"> <!-window.print(; //--> </script> When a syntax error occurs in JavaScript, only the code contained within the same thread as the syntax error is affected and the rest of the code in other threads gets executed assuming nothing in them depends on the code containing the error. Runtime Errors Runtime errors, also called compilation/interpretation). exceptions, occur during execution (after For example, the following line causes a runtime error because here the syntax is correct, but at runtime, it is trying to call a method that does not exist. <script type="text/javascript"> <!-window.printme(); //--> </script> Exceptions also affect the thread in which they occur, allowing other JavaScript threads to continue normal execution. 343 Javascript Logical Errors Logic errors can be the most difficult type of errors to track down. These errors are not the result of a syntax or runtime error. Instead, they occur when you make a mistake in the logic that drives your script and you do not get the result you expected. You cannot catch those errors, because it depends on your business requirement what type of logic you want to put in your program. The try...catch...finally Statement The latest versions of JavaScript added exception handling capabilities. JavaScript implements the try...catch...finally construct as well as the throw operator to handle exceptions. You can catch programmer-generated and runtime exceptions, but you cannot catch JavaScript syntax errors. Here is the try...catch...finally block syntax: <script type="text/javascript"> <!-try { // Code to run [break;] } catch ( e ) { // Code to run if an exception occurs [break;] }[ finally { // Code that is always executed regardless of // an exception occurring }] //--> </script> The try block must be followed by either exactly one catch block or one finally block (or one of both). When an exception occurs in the try block, the exception is placed in e and the catch block is executed. The optional finally block executes unconditionally after try/catch. 344 Javascript Example Here is an example where we are trying to call a non-existing function which in turn is raising an exception. Let us see how it behaves without try...catch. <html> <head> <script type="text/javascript"> <!-function myFunc() { var a = 100; document.write ("Value of variable a is : " + a ); } //--> </script> </head> <body> <p>Click the following to see the result:</p> <form> <input type="button" value="Click Me" onclick="myFunc();" /> </form> <p>Error will happen and depending on your browser it will give different result.</p> </body> </html> Output Click the following to see the result: Click Me Error will happen and depending on your browser it will give different result. 345 Javascript Now let us try to catch this exception using try...catch and display a userfriendly message. You can also suppress this message, if you want to hide this error from a user. <html> <head> <script type="text/javascript"> <!-function myFunc() { var a = 100; try { document.write ("Value of variable a is : " + a ); } catch ( e ) { document.write ("Error: " + e.description ); } } //--> </script> </head> <body> <p>Click the following to see the result:</p> <form> <input type="button" value="Click Me" onclick="myFunc();" /> </form> </body> </html> Output Click the following to see the result: Click Me 346 Javascript You can use a finally block which will always execute unconditionally after the try/catch. Here is an example. Example <html> <head> <script type="text/javascript"> <!-function myFunc() { var a = 100; try { document.write ("Value of variable a is : " + a ); }catch ( e ) { document.write ("Error: " + e.description ); }finally { document.write ("Finally block will always execute!" ); } } //--> </script> </head> <body> <p>Click the following to see the result:</p> <form> <input type="button" value="Click Me" onclick="myFunc();" /> </form> <p>Try running after fixing the problem with method name.</p> </body> </html> 347 Javascript Output Click the following to see the result: Click Me Try running after fixing the problem with method name. The throw Statement You can use a throw statement to raise your built-in exceptions or your customized exceptions. Later these exceptions can be captured and you can take an appropriate action. Example The following example demonstrates how to use a throw statement. <html> <head> <script type="text/javascript"> <!-function myFunc() { var a = 100; var b = 0; try{ if ( b == 0 ){ throw( "Divide by zero error." ); }else{ var c = a / b; } }catch ( e ) { document.write ("Error: " + e ); } } //--> </script> 348 Javascript </head> <body> <p>Click the following to see the result:</p> <form> <input type="button" value="Click Me" onclick="myFunc();" /> </form> </body> </html> Output Click the following to see the result: Click Me You can raise an exception in one function using a string, integer, Boolean, or an object and then you can capture that exception either in the same function as we did above, or in another function using a try...catch block. The onerror( ) Method The onerror event handler was the first feature to facilitate error handling in JavaScript. The error event is fired on the window object whenever an exception occurs on the page. Example <html> <head> <script type="text/javascript"> <!-window.onerror = function () { document.write ("An error occurred."); } //--> </script> </head> <body> 349 Javascript <p>Click the following to see the result:</p> <form> <input type="button" value="Click Me" onclick="myFunc();" /> </form> </body> </html> Output Click the following to see the result: Click Me The onerror event handler provides three pieces of information to identify the exact nature of the error:  Error message: The same message that the browser would display for the given error  URL: The file in which the error occurred  Line number: The line number in the given URL that caused the error Here is the example to show how to extract this information. Example <html> <head> <script type="text/javascript"> <!-window.onerror = function (msg, url, line) { document.write ("Message : " + msg ); document.write ("url : " + url ); document.write ("Line number : " + line ); } //--> </script> </head> <body> 350 Javascript <p>Click the following to see the result:</p> <form> <input type="button" value="Click Me" onclick="myFunc();" /> </form> </body> </html> Output Click the following to see the result: Click Me You can display extracted information in whatever way you think it is better. You can use an onerror method, as shown below, to display an error message in case there is any problem in loading an image. <img src="myimage.gif" onerror = "alert('An error occurred loading the image.')" /> You can use onerror with many HTML tags to display appropriate messages in case of errors. 351 30. FORM VALIDATION Javascript Form validation normally used to occur at the server, after the client had entered all the necessary data and then pressed the Submit button. If the data entered by a client was incorrect or was simply missing, the server would have to send all the data back to the client and request that the form be resubmitted with correct information. This was really a lengthy process which used to put a lot of burden on the server. JavaScript provides a way to validate form's data on the client's computer before sending it to the web server. Form validation generally performs two functions.  Basic Validation - First of all, the form must be checked to make sure all the mandatory fields are filled in. It would require just a loop through each field in the form and check for data.  Data Format Validation - Secondly, the data that is entered must be checked for correct form and value. Your code must include appropriate logic to test correctness of data. Example We will take an example to understand the process of validation. Here is a simple form in html format. <html> <head> <title>Form Validation</title> <script type="text/javascript"> <!-// Form validation code will come here. //--> </script> </head> <body> <form action="/cgi-bin/test.cgi" name="myForm" onsubmit="return(validate());"> <table cellspacing="2" cellpadding="2" border="1"> <tr> <td align="right">Name</td> 352 Javascript <td><input type="text" name="Name" /></td> </tr> <tr> <td align="right">EMail</td> <td><input type="text" name="EMail" /></td> </tr> <tr> <td align="right">Zip Code</td> <td><input type="text" name="Zip" /></td> </tr> <tr> <td align="right">Country</td> <td> <select name="Country"> <option value="-1" selected>[choose yours]</option> <option value="1">USA</option> <option value="2">UK</option> <option value="3">INDIA</option> </select> </td> </tr> <tr> <td align="right"></td> <td><input type="submit" value="Submit" /></td> </tr> </table> </form> </body> </html> Output 353 Javascript Basic Form Validation First let us see how to do a basic form validation. In the above form, we are calling validate() to validate data when onsubmit event is occurring. The following code shows the implementation of this validate() function. <script type="text/javascript"> <!-// Form validation code will come here. function validate() { if( document.myForm.Name.value == "" ) { alert( "Please provide your name!" ); document.myForm.Name.focus() ; return false; } if( document.myForm.EMail.value == "" ) { alert( "Please provide your Email!" ); document.myForm.EMail.focus() ; return false; 354 Javascript } if( document.myForm.Zip.value == "" || isNaN( document.myForm.Zip.value ) || document.myForm.Zip.value.length != 5 ) { alert( "Please provide a zip in the format #####." ); document.myForm.Zip.focus() ; return false; } if( document.myForm.Country.value == "-1" ) { alert( "Please provide your country!" ); return false; } return( true ); } //--> </script> Data Format Validation Now we will see how we can validate our entered form data before submitting it to the web server. The following example shows how to validate an entered email address. An email address must contain at least a ‘@’ sign and a dot (.). Also, the ‘@’ must not be the first character of the email address, and the last dot must at least be one character after the ‘@’ sign. Example Try the following code for email validation. <script type="text/javascript"> <!-function validateEmail() { 355 Javascript var emailID = document.myForm.EMail.value; atpos = emailID.indexOf("@"); dotpos = emailID.lastIndexOf("."); if (atpos < 1 || ( dotpos - atpos < 2 )) { alert("Please enter correct email ID") document.myForm.EMail.focus() ; return false; } return( true ); } //--> </script> 356 31. Javascript ANIMATION You can use JavaScript to create a complex animation having, but not limited to, the following elements:      Fireworks Fade Effect Roll-in or Roll-out Page-in or Page-out Object movements You might be interested library: Script.Aculo.us. in existing JavaScript based animation This tutorial provides a basic understanding of how to use JavaScript to create an animation. JavaScript can be used to move a number of DOM elements (<img />, <div>, or any other HTML element) around the page according to some sort of pattern determined by a logical equation or function. JavaScript provides the following two functions to be frequently used in animation programs.    setTimeout (function, duration) - This function calls function after duration milliseconds from now. setInterval (function, duration) - This function calls function after every duration milliseconds. clearTimeout (setTimeout_variable) - This function clears any timer set by the setTimeout() function. JavaScript can also set a number of attributes of a DOM object including its position on the screen. You can set top and left attribute of an object to position it anywhere on the screen. Here is its syntax. // Set distance from left edge of the screen. object.style.left = distance in pixels or points; or // Set distance from top edge of the screen. object.style.top = distance in pixels or points; 357 Javascript Manual Animation So let's implement one simple animation using DOM object properties and JavaScript functions as follows. The following list contains different DOM methods.  We are using the JavaScript function getElementById() to get a DOM object and then assigning it to a global variable imgObj.  We have defined an initialization function init() to initialize imgObj where we have set its position and left attributes.  We are calling initialization function at the time of window load.  Finally, we are calling moveRight() function to increase the left distance by 10 pixels. You could also set it to a negative value to move it to the left side. Example Try the following example. <html> <head> <title>JavaScript Animation</title> <script type="text/javascript"> <!-var imgObj = null; function init(){ imgObj = document.getElementById('myImage'); imgObj.style.position= 'relative'; imgObj.style.left = '0px'; } function moveRight(){ imgObj.style.left = parseInt(imgObj.style.left) + 10 + 'px'; } window.onload =init; //--> </script> </head> <body> 358 Javascript <form> <img id="myImage" src="/images/html.gif" /> <p>Click button below to move the image to right</p> <input type="button" value="Click Me" onclick="moveRight();" /> </form> </body> </html> Output It is not possible to show animation in this tutorial. But you can Try it here. Automated Animation In the above example, we saw how an image moves to right with every click. We can automate this process by using the JavaScript function setTimeout() as follows. Here we have added more methods. So let's see what is new here:  The moveRight() function is calling setTimeout() function to set the position of imgObj.  We have added a new function stop() to clear the timer by setTimeout() function and to set the object at its initial position. set Example Try the following example code. <html> <head> <title>JavaScript Animation</title> <script type="text/javascript"> <!-var imgObj = null; var animate ; function init(){ imgObj = document.getElementById('myImage'); imgObj.style.position= 'relative'; imgObj.style.left = '0px'; 359 Javascript } function moveRight(){ imgObj.style.left = parseInt(imgObj.style.left) + 10 + 'px'; animate = setTimeout(moveRight,20); // call moveRight in 20msec } function stop(){ clearTimeout(animate); imgObj.style.left = '0px'; } window.onload =init; //--> </script> </head> <body> <form> <img id="myImage" src="/images/html.gif" /> <p>Click the buttons below to handle animation</p> <input type="button" value="Start" onclick="moveRight();" /> <input type="button" value="Stop" onclick="stop();" /> </form> </body> </html> It is not possible to show animation in this tutorial. But you can Try it here. Rollover with a Mouse Event Here is a simple example showing image rollover with a mouse event. Let's see what we are using in the following example:   At the time of loading this page, the ‘if’ statement checks for the existence of the image object. If the image object is unavailable, this block will not be executed. The Image() constructor creates and preloads a new image object called image1. 360 Javascript  The src property is assigned the name of the external image file called /images/html.gif.  Similarly, we have created image2 object and assigned /images/http.gif in this object.  The # (hash mark) disables the link so that the browser does not try to go to a URL when clicked. This link is an image.  The onMouseOver event handler is triggered when the user's mouse moves onto the link, and the onMouseOut event handler is triggered when the user's mouse moves away from the link (image).  When the mouse moves over the image, the HTTP image changes from the first image to the second one. When the mouse is moved away from the image, the original image is displayed.  When the mouse is moved away from the link, the initial image html.gif will reappear on the screen. <html> <head> <title>Rollover with a Mouse Events</title> <script type="text/javascript"> <!-if(document.images){ var image1 = new Image(); // Preload an image image1.src = "/images/html.gif"; var image2 = new Image(); // Preload second image image2.src = "/images/http.gif"; } //--> </script> </head> <body> <p>Move your mouse over the image to see the result</p> <a href="#" onMouseOver="document.myImage.src=image2.src;" onMouseOut="document.myImage.src=image1.src;"> <img name="myImage" src="/images/html.gif" /> </a> </body> 361 Javascript </html> It is not possible to show animation in this tutorial. But you can Try it here. 362 32. MULTIMEDIA Javascript The JavaScript navigator object includes a child object called plugins. This object is an array, with one entry for each plug-in installed on the browser. The navigator.plugins object is supported only by Netscape, Firefox, and Mozilla only. Example Here is an example that shows how to list down all the plug-on installed in your browser: <html> <head> <title>List of Plug-Ins</title> </head> <body> <table border="1"> <tr><th>Plug-in Name</th><th>Filename</th><th>Description</th></tr> <script LANGUAGE="JavaScript" type="text/javascript"> for (i=0; i<navigator.plugins.length; i++) { document.write("<tr><td>"); document.write(navigator.plugins[i].name); document.write("</td><td>"); document.write(navigator.plugins[i].filename); document.write("</td><td>"); document.write(navigator.plugins[i].description); document.write("</td></tr>"); } </script> </table> </body> </html> 363 Javascript Output Checking for Plug-Ins Each plug-in has an entry in the array. Each entry has the following properties:     name - is the name of the plug-in. filename - is the executable file that was loaded to install the plug-in. description - is a description of the plug-in, supplied by the developer. mimeTypes - is an array with one entry for each MIME type supported by the plug-in. You can use these properties in a script to find out the installed plug-ins, and then using JavaScript, you can play appropriate multimedia file. Take a look at the following example. <html> <head> <title>Using Plug-Ins</title> </head> <body> <script language="JavaScript" type="text/javascript"> media = navigator.mimeTypes["video/quicktime"]; if (media){ document.write("<embed src='quick.mov' height=100 width=100>"); } else{ 364 Javascript document.write("<img src='quick.gif' height=100 width=100>"); } </script> </body> </html> NOTE: Here we are using HTML <embed> tag to embed a multimedia file. Controlling Multimedia Let us take a real example which works in almost all the browsers. <html> <head> <title>Using Embeded Object</title> <script type="text/javascript"> <!-function play() { if (!document.demo.IsPlaying()){ document.demo.Play(); } } function stop() { if (document.demo.IsPlaying()){ document.demo.StopPlay(); } } function rewind() if (document.demo.IsPlaying()){ document.demo.StopPlay(); } document.demo.Rewind(); } 365 Javascript //--> </script> </head> <body> <embed id="demo" name="demo" src="http://www.amrood.com/games/kumite.swf" width="318" height="300" play="false" loop="false" pluginspage="http://www.macromedia.com/go/getflashplayer" swliveconnect="true"> </embed> <form name="form" id="form" action="#" method="get"> <input type="button" value="Start" onclick="play();" /> <input type="button" value="Stop" onclick="stop();" /> <input type="button" value="Rewind" onclick="rewind();" /> </form> </body> </html> If you are using Mozilla, Firefox or Netscape, then Try it yourself. 366 33. DEBUGGING Javascript Every now and then, developers commit mistakes while coding. A mistake in a program or a script is referred to as a bug. The process of finding and fixing bugs is called debugging and is a normal part of the development process. This section covers tools and techniques that can help you with debugging tasks. Error Messages in IE The most basic way to track down errors is by turning on error information in your browser. By default, Internet Explorer shows an error icon in the status bar when an error occurs on the page. Double-clicking this icon takes you to a dialog box showing information about the specific error that occurred. Since this icon is easy to overlook, Internet Explorer gives you the option to automatically show the Error dialog box whenever an error occurs. To enable this option, select Tools --> Internet Options --> Advanced tab and then finally check the “Display a Notification about Every Script Error” box option as shown below. 367 Javascript Error Messages in Firefox or Mozilla Other browsers like Firefox, Netscape, and Mozilla send error messages to a special window called the JavaScript Console or Error Console. To view the console, select Tools --> Error Console or Web Development. Unfortunately, since these browsers give no visual indication when an error occurs, you must keep the Console open and watch for errors as your script executes. 368 Javascript Error Notifications Error notifications that show up on Console or through Internet Explorer dialog boxes are the result of both syntax and runtime errors. These error notification include the line number at which the error occurred. If you are using Firefox, then you can click on the error available in the error console to go to the exact line in the script having error. How to Debug a Script There are various ways to debug your JavaScript: Use a JavaScript Validator One way to check your JavaScript code for strange bugs is to run it through a program that checks it to make sure it is valid and that it follows the official syntax rules of the language. These programs are called validating parsers or just validators for short, and often come with commercial HTML and JavaScript editors. The most convenient validator for JavaScript is Douglas Crockford's JavaScript Lint, which is available for free at Douglas Crockford's JavaScript Lint. Simply visit that web page, paste your JavaScript (Only JavaScript) code into the text area provided, and click the jslint button. This program will parse through your JavaScript code, ensuring that all the variable and function definitions follow the correct syntax. It will also check JavaScript statements, such as if and while, to ensure they too follow the correct format Add Debugging Code to Your Programs You can use the alert() or document.write() methods in your program to debug your code. For example, you might write something as follows: ar debugging = true; var whichImage = "widget"; if( debugging ) alert( "Calls swapImage() with argument: " + whichImage ); var swapStatus = swapImage( whichImage ); if( debugging ) alert( "Exits swapImage() with swapStatus=" + swapStatus ); By examining the content and order of the alert() as they appear, you can examine the health of your program very easily. 369 Javascript Use a JavaScript Debugger A debugger is an application that places all aspects of script execution under the control of the programmer. Debuggers provide fine-grained control over the state of the script through an interface that allows you to examine and set values as well as control the flow of execution. Once a script has been loaded into a debugger, it can be run one line at a time or instructed to halt at certain breakpoints. Once execution is halted, the programmer can examine the state of the script and its variables in order to determine if something is amiss. You can also watch variables for changes in their values. The latest version of the Mozilla JavaScript Debugger (code-named Venkman) for both Mozilla and Netscape browsers can be downloaded at http://www.hacksrus.com/~ginda/venkman. Useful Tips for Developers You can keep the following tips in mind to reduce the number of errors in your scripts and simplify the debugging process:        Use plenty of comments. Comments enable you to explain why you wrote the script the way you did and to explain particularly difficult sections of code. Always use indentation to make your code easy to read. Indenting statements also makes it easier for you to match up beginning and ending tags, curly braces, and other HTML and script elements. Write modular code. Whenever possible, group your statements into functions. Functions let you group related statements, and test and reuse portions of code with minimal effort. Be consistent in the way you name your variables and functions. Try using names that are long enough to be meaningful and that describe the contents of the variable or the purpose of the function. Use consistent syntax when naming variables and functions. In other words, keep them all lowercase or all uppercase; if you prefer Camel-Back notation, use it consistently. Test long scripts in a modular fashion. In other words, do not try to write the entire script before testing any portion of it. Write a piece and get it to work before adding the next portion of code. Use descriptive variable and function names and avoid using singlecharacter names. 370 Javascript    Watch your quotation marks. Remember that quotation marks are used in pairs around strings and that both quotation marks must be of the same style (either single or double). Watch your equal signs. You should not used a single = for comparison purpose. Declare variables explicitly using the var keyword. 371 34. IMAGE MAP Javascript You can use JavaScript to create client-side image map. Client-side image maps are enabled by the usemap attribute for the <img /> tag and defined by special <map> and <area> extension tags. The image that is going to form the map is inserted into the page using the <img /> element as normal, except that it carries an extra attribute called usemap. The value of the usemap attribute is the value of the name attribute on the <map> element, which you are about to meet, preceded by a pound or hash sign. The <map> element actually creates the map for the image and usually follows directly after the <img /> element. It acts as a container for the <area /> elements that actually define the clickable hotspots. The <map> element carries only one attribute, the name attribute, which is the name that identifies the map. This is how the <img /> element knows which <map> element to use. The <area> element specifies the shape and the coordinates that define the boundaries of each clickable hotspot. The following code combines imagemaps and JavaScript to produce a message in a text box when the mouse is moved over different parts of an image. <html> <head> <title>Using JavaScript Image Map</title> <script type="text/javascript"> <!-function showTutorial(name){ document.myform.stage.value = name } //--> </script> </head> <body> <form name="myform"> <input type="text" name="stage" size="20" /> </form> 372 Javascript <!-- Create Mappings --> <img src="/images/usemap.gif" alt="HTML Map" border="0" usemap="#tutorials"/> <map name="tutorials"> <area shape="poly" coords="74,0,113,29,98,72,52,72,38,27" href="/perl/index.htm" alt="Perl Tutorial" target="_self" onMouseOver="showTutorial('perl')" onMouseOut="showTutorial('')"/> <area shape="rect" coords="22,83,126,125" href="/html/index.htm" alt="HTML Tutorial" target="_self" onMouseOver="showTutorial('html')" onMouseOut="showTutorial('')"/> <area shape="circle" coords="73,168,32" href="/php/index.htm" alt="PHP Tutorial" target="_self" onMouseOver="showTutorial('php')" onMouseOut="showTutorial('')"/> </map> </body> </html> 373 Javascript Output You can feel the map concept by placing the mouse cursor on the image object. PERL HTML PHP 374 35. BROWSERS Javascript It is important to understand the differences between different browsers in order to handle each in the way it is expected. So it is important to know which browser your web page is running in. To get information about the browser your webpage is currently running in, use the built-in navigator object. Navigator Properties There are several Navigator related properties that you can use in your Web page. The following is a list of the names and descriptions of each. S.No Property and Description appCodeName 1 This property is a string that contains the code name of the browser, Netscape for Netscape and Microsoft Internet Explorer for Internet Explorer. appVersion 2 This property is a string that contains the version of the browser as well as other useful information such as its language and compatibility. language 3 This property contains the two-letter abbreviation for the language that is used by the browser. Netscape only. mimTypes[] 4 This property is an array that contains all MIME types supported by the client. Netscape only. platform[] 5 This property is a string that contains the platform for which the browser was compiled."Win32" for 32-bit Windows operating systems 375 Javascript plugins[] 6 This property is an array containing all the plug-ins that have been installed on the client. Netscape only. userAgent[] 7 This property is a string that contains the code name and version of the browser. This value is sent to the originating server to identify the client. Navigator Methods There are several Navigator-specific methods. Here is a list of their names and descriptions. S.No Method and Description javaEnabled() 1 This method determines if JavaScript is enabled in the client. If JavaScript is enabled, this method returns true; otherwise, it returns false. plugings.refresh 2 This method makes newly installed plug-ins available and populates the plugins array with all new plug-in names. Netscape only. preference(name,value) 3 This method allows a signed script to get and set some Netscape preferences. If the second parameter is omitted, this method will return the value of the specified preference; otherwise, it sets the value. Netscape only. taintEnabled() 4 This method returns true if data tainting is enabled; false otherwise. 376 Javascript Browser Detection There is a simple JavaScript which can be used to find out the name of a browser and then accordingly an HTML page can be served to the user. <html> <head> <title>Browser Detection Example</title> </head> <body> <script type="text/javascript"> <!-var userAgent = navigator.userAgent; var opera = (userAgent.indexOf('Opera') != -1); var ie = (userAgent.indexOf('MSIE') != -1); var gecko = (userAgent.indexOf('Gecko') != -1); var netscape = (userAgent.indexOf('Mozilla') != -1); var version = navigator.appVersion; if (opera){ document.write("Opera based browser"); // Keep your opera specific URL here. }else if (gecko){ document.write("Mozilla based browser"); // Keep your gecko specific URL here. }else if (ie){ document.write("IE based browser"); // Keep your IE specific URL here. }else if (netscape){ document.write("Netscape based browser"); // Keep your Netscape specific URL here. }else{ document.write("Unknown browser"); } // You can include version to along with any above condition. 377 Javascript document.write("<br /> Browser version info : " + version ); //--> </script> </body> </html> Output Mozilla based browser Browser version info : 5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.101 Safari/537.36 378