How to add JavaScript onClick handler to an embedded html object?

You have to implement onclick inside the svg and link it to the external JavaScript function using javascript inside the svg. See the SVG wiki for examples.

Update: Apparently the SVG wiki is no more. No surprise that the best references I can now (quickly) find are on StackOverflow itself.

This answer describes how to implement onclick inside the svg.

Use either javascript binding (Mario Menger answered that already).

If you can't or won't use the binding, you can use what xil3 answered with one modification:

Use an empty anchor tag <a href="javascript:someFunc()"></a> as the click consumer. Set it's z-index and position/size so it positioned over the svg object (for cross-browser compatibility).