How to add an animated svg via javascript?

Question

<svg width="5cm" height="3cm"  viewBox="0 0 500 300">
<path id="path1" d="M100,250 C 100,50 400,50 400,250"
    fill="none" stroke="blue" stroke-width="7.06"  />
<circle r="17.64" fill="red">
<animateMotion dur="6s" repeatCount="1" rotate="auto" >
   <mpath xlink:href="#path1"/>
</animateMotion>
</circle>
</svg>

If I write the svg in plain html/svg file, it works fine, the circle animates correctly. But if I add the circle element dynamically via javascript, circle was added, but it didn't animate. What's wrong? js code:

    var svg = $("svg"); //use jquery
var circle = document.createElementNS("http://www.w3.org/2000/svg","circle");
circle.setAttribute("r", "5");
circle.setAttribute("fill", "red");
var ani = document.createElementNS("http://www.w3.org/2000/svg","animateMotion");
ani.setAttribute("dur", "26s");
ani.setAttribute("repeatCount", "indefinite");
ani.setAttribute("rotate", "auto");
var mpath = document.createElementNS("http://www.w3.org/2000/svg","mpath");
mpath.setAttribute("xlink:href", "#path1");
ani.appendChild(mpath);
circle.appendChild(ani);
svg.append(circle);

Answer 1

Use setAttributeNS on "mpath" instead of setAttribute.

mpath.setAttributeNS("http://www.w3.org/1999/xlink", "href", "#path1");

Here's a demo: http://jsfiddle.net/zh553/

Answer 2

Agree with using setAttributeNS on "mpath" instead of setAttribute.

However at least for Chrome (and other WebKit based browsers?) it seems to be necessary to pay attention to http://www.w3.org/TR/DOM-Level-2-Core/core.html#ID-ElSetAttrNS where it says the second parameter is the qualifiedName, the qualified name of the attribute to create or alter.

mpath.setAttributeNS("http://www.w3.org/1999/xlink", "xlink:href", "#path1");

Or, if needed, more generically:

mpath.setAttributeNS("http://www.w3.org/1999/xlink",
                     mpath.lookupPrefix("http://www.w3.org/1999/xlink") + ":href",
                     "#path1");

Also discussed at https://bugs.webkit.org/show_bug.cgi?id=22958