Javascript unique array items

Question

I have an array like this:

var data = [
            { Group: 'A', Name: 'SD' },
            { Group: 'B', Name: 'FI' },
            { Group: 'A', Name: 'MM' },            
            { Group: 'B', Name: 'CO' }
           ];

I want to get only the unique Group values in an array like:

var unique = ['A','B'];

I looked at some of the examples on SO but I don't understand them. Can anyone tell me how I should do this?

Answer 1

var data = [
             { Group: 'A', Name: 'SD' },
             { Group: 'B', Name: 'FI' },
             { Group: 'A', Name: 'MM' },            
             { Group: 'B', Name: 'CO' }
           ];

var set = {};
for (var i = 0; i < data.length; i++)
    set[data[i].Group] = 1;

var arr = [];
for(var key in set)
    arr.push(key);

alert(arr);

Answer 2

If you are using ES6/ES2015 or later you can do it this way:

var unique = [...new Set(data.map(item => item.Group))];

Here is an example on how to do it.