Alternative for "for, EVENT" that works on Mozilla Firefox?


Reaction score
So I was looking through the Virtools documentation. For those who don't know, Virtools has a plugin which can be used in sync with Javascript. But the documentation is old. Like, Netscape old. Anyways, I happened upon this code snippet, and the doc said this will only work in Internet Explorer:
<script language="JavaScript" for="Virtools" EVENT="CompositionLoadedEvent(param)">
  alert("CompositionLoadedEvent = " + param);
And, true to it's word, it does not work in Mozilla Firefox 26 Beta. Although it does work in IE10.
But as I said, the doc is old, and the first question I asked myself was "what's with the for attribute on the script tag?" I mean, I've seen it used on labels, but never on a script tag. And the EVENT attribute... again, what's up with that? I had never seen that before even off of a script tag!
Mozilla's wiki, naturally, didn't have anything about it in their specifications, but MSDN did here:
So apparently, Virtools (which is indeed the ID of the plugin) is triggering an event called CompositionLoadedEvent, and this is some sort of crazy event handler for it.
Does anyone know of a more modern workaround that will work in Mozilla Firefox? I can't modify the event handler, it's part of the plugin, but using addEventListener or document.Virtools.CompositionLoadedEvent didn't seem to work either.
Thank you in advance