onunload didn't work with JSeventFunCalls but might be required, for example with Google Maps to fix some memory leaks with IE.
Attached is a patch that adds that feature just like onload:
(issue imported from #M4701)
Updated by Christoph Koehler over 14 years ago
Not sure since both are valid and I am not a JS guy. I use it for Google Maps which requires the onload stuff to be in the body tag. So as long as I can still do that, I am good.
If they are different (couldn't find anything on Google about that), we could just add them as an option instead of including them all the time automatically.
Updated by Oliver Hader over 14 years ago
Have a look how this is implemented in prototype.js event handlers ("_observeAndCache"):