(Embed and) Refer to an external SVG via D3 and/or javascript

Question

I have an .svg file and want to embed it in the svg strucure of my d3-graphic.

I also need to reference all paths/polygons attached to g-elements via an id of certain g elements.

I tried different ways to to embed and reference the svg (g's), but it didn't work for some reasons:

(1) first attempt

// Firefox displays my svg but when i open it with Chrome the svg     
//is not displayed (just default placeholder icon)
// I can't reference the svg-g id's with d3.select functions. 
main_chart_svg
        .append("svg:image")
        .attr("xlink:href", "mySVGpicture.svg")
        .attr("x", "50")
        .attr("y", "50")
        .attr("width", "500")
        .attr("height", "500");  

main_chart_svg.select("#anIdWhichIsInTheSvgFile").remove(); //// This doesn't work

(2) second attempt

// This displays the svg but -not- inside my main-chart-svg. I want to keep the graphic   
//things seperate to html-stuff.
d3.xml("mySVGpicture.svg", "image/svg+xml", function(xml) {
        document.body.appendChild(xml.documentElement);
    });
//----------or----------//
    d3.select("body")
        .append("object")
        .attr("data", "mySVGpicture.svg")
        .attr("width", 500)
        .attr("height", 500)
        .attr("type", "image/svg+xml");

d3.select("#anIdThatIsInTheSvgFile").remove(); //does not work.

(3) The svg-file looks something like that:

<?xml version="1.0" encoding="utf-8"?>
<!-- Generator: Adobe Illustrator 15.1.0, SVG Export Plug-In . SVG Version: 6.00 Build 0)  -->
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" width="400px"
     height="400px" viewBox="0 0 400 400" enable-background="new 0 0 400 400" xml:space="preserve">
    <g id="anIdWhichIsInTheSvgFile">
        <g id="DE">
            <path fill="#FEDCBD" d="M215.958,160.554c0,0-0.082, ... ,1.145
                l0.865,0.656L215.958,160.554z"/>
            <path fill="#FEDCBD" d="M208.682,155.88l1.246,1.031c0,0,0.191,0.283, ... ,0.572L208.682,155.88z"/>
            <polygon fill="#FEDCBD" points="190.76,153.007 190.678, ... ,153.938 
                191.427,152.906"/>
            <polygon fill="#FEDCBD" points="170.088,151.015 169.888,150.067 169.125,150.075 168.846,150.836 169.521,151.588"/>
            <polygon fill="#FEDCBD" points="168.953,152.067 168.188,151.505 168.674,152.639"/>
            <polygon fill="#FEDCBD" points="170.105,153.099 170.666,152.052 170.002,152.248"/>
    </g>
    <g id="anIdThatIsInTheSvgFile">
    ...
    </g>
</svg>

Answer 1

There's a better solution.

I hadn't realized that the d3.xml() function returns a read-in xml file as a document fragment (as opposed to converting it to JSON). In other words, it returns a ready-made DOM tree that can be inserted within you main document's DOM wherever you need it.

Knowing that (and knowing that stand-alone SVG files are also XML files), this is likely the most reliable approach for adding external SVG content to your webpage:

d3.xml("http://upload.wikimedia.org/wikipedia/commons/a/a0/Circle_-_black_simple.svg", 
        function(error, documentFragment) {

    if (error) {console.log(error); return;}

    var svgNode = documentFragment
                .getElementsByTagName("svg")[0];
    //use plain Javascript to extract the node

    main_chart_svg.node().appendChild(svgNode);
    //d3's selection.node() returns the DOM node, so we
    //can use plain Javascript to append content

    var innerSVG = main_chart_svg.select("svg");

    innerSVG.transition().duration(1000).delay(1000)
          .select("circle")
          .attr("r", 100);

});

Fiddle here: http://jsfiddle.net/J8sp3/4/

Notice in particular that (a) I am adding the content to an existing SVG, and (b) I am not deleting any of that SVG's current content.

Of course, you can also add the SVG to a <div> or any other element that can contain it: http://jsfiddle.net/J8sp3/3/

This method should work in any browser that supports SVG. I even tried it in IE8, and the DOM structure is correct even if IE8 doesn't know how to draw circles and rectangles!

@Seb, please unselect the previous answer at pick this one as the accepted answer.