You can include the SVG file directly in your HTML, no need to load it in Javascript. For example:
<object id="mySVG" data="my.svg" type="image/svg+xml"></object>
The only thing to keep in mind with this is that you end up with two DOMs in your document (the main HTML one and the embedded SVG one) and CSS selectors don't cross DOM boundaries. That is, d3.select("#IDinSVG")
probably won't work, but something like d3.select(d3.select("#mySVG").node().getDocumentElement()).select("#IDinSVG")
should.