An SVG is all you need

The JS is exposed in the full page's context the same as if you included a <script> under a <div> instead of <svg>. In much the same way, whether the <script> is before or after the <svg> tag doesn't matter - it's just a script working on a single DOM (with different namespaces for certain elements) either way.

I guess the point is you can give a single .svg file with the js inside. But you can also give a single .html with svg and js inside.