Chrome Breakpoint On Radio Doesn't Fire

I have a page where some JavaScript modifies a radio button to be not checked and another to be checked -- the HTML source contains the right checked attributes but when inspecting

Solution 1:

Phil's comment is helpful but it needs just a little love. First, check the Async checkbox

in the Sources tab just next to the Call Stack. Otherwise you won't get a useful call stack. Then add this snippet:

<script>var debugel  = document.getElementById("edit-field-slideshow-media-type-und-images");
Object.observe(debugel, function(changes) {
  console.log(changes);
  debugger;
});
</script>

Between the console and the debugger you have a reasonable chance to figure out what happens.