User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:80.0) Gecko/20100101 Firefox/80.0

Steps to reproduce:

window.onbeforeunload = function(){
return 'Los cambios no guardados se perderan, ¿Desea salir?';
}
window.onunload = function(){
window.opener.document.getElementById('alert-content').innerHTML='';
window.opener.document.getElementById('bttsearchdoc').click();

									}

Actual results:

since version 79 of firefox the javascript "onunload" event does not work. No execute the action inside event "onunload". I have verified that it works well in firefox version 78 and olders, but in the version 79 and 80 it does not work. This is a serious problem for some web apps. Now, I have started to use Chrome due to this issue and I have always liked firefox more.

Expected results:

This should do the actions inside the "onunload" event. Well, in all versions of firefox before 79 it has always worked well.

Thanks for reporting this issue! Could you share a test page and steps so we can try to reproduce this issue on our end? Thanks.

Yes, I make a test page with the problem:

https://application.onnix.es:880/onnix/application/views/es/test_page_1

This page, show a link, that when you click open other page 2 in other tab. So when you close Page 2, the text "Link Clicked" of page 1 shoud be cleaned, but is not working with firefox. I have tested the same in Chrome and it working correctly.

Thanks, I hope you can solve it quickly, because it is very important for me and for many web pages.

This is not related unload event, but the opener setup for anchors with target=_blank.
See https://www.fxsitecompat.dev/en-CA/docs/2020/target-blank-on-anchors-now-implies-rel-noopener/.

I have added the attribute rel="opener" in my href link and now working correctly again.

Thank you very much. My problem is solved.