having problems selecting svg child elements using d3

Question

I have an svg that I'm trying to access and modify using d3.js. The svg file name is us-map.svg. I've included a reference to the svg in my html like this:

<object id="imgMap" data="us-map.svg" type="image/svg+xml">
</object>

I can select imgMap in my chrome watch panel like this:

var imgMap = d3.select('#imgMap')

However, I'm not able to select child elements. For example, my imgMap svg has several child <g> elements but the child elements are not returned with this function:

d3.select('#imgMap').selectAll('g')

Am I missing something here? I was thinking that d3 could be used to traverse and manipulate an existing svg?

Answer 1

I was thinking that d3 could be used to traverse and manipulate an existing SVG

This is pretty much what d3 does best. But when you write:

d3.select('#imgMap')

You are not selecting the SVG (unless you have an SVG with id = "imgMap", which is not your case). You're using an <object>. Thus, you have to write:

var mySVG = d3.select(document.getElementById("imgMap").contentDocument);

And then select your groups using mySVG.

var myGroups = mySVG.selectAll("g");

Have in mind that this selection only works after the object has been loaded.

Source: https://benfrain.com/selecting-svg-inside-tags-with-javascript/

EDIT:

As requested by the OP, this is a basic working demo: https://plnkr.co/edit/RJOznJROiqTpo5dm9M7L?p=preview

In this plunkr, "mysvg.svg" is an external file (in your code, you'll have to provide the correct path). The code finds the SVG:

var mySVG = d3.select(document.getElementById("imgMap").contentDocument);

And then selects the blue circle inside the SVG, moving it to the right:

var myCircle = mySVG.select("#blueCircle"); 
myCircle.transition().duration(2000).attr("cx", 180);

Pay attention to this: I set a setTimeout of 1000ms, just to make sure that the object is loaded before the code runs.