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no way to disable the javascript window.onbeforeunload()

  • 5 replies
  • 35 have this problem
  • 3401 views
  • Last reply by alecail

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Firefox has given the options for the user to control how certain javascript functions can be used. I came across a horrible use of window.onbeforeunload() which keeps firefox from closing a tab, and therefore also quiting. A manual kill is required to close a page with the following code: (just open in firefox to test)

<title>test</title><script type="text/javascript">window.onbeforeunload=function(){return 'PRESS ESCAPE OR CLOSE THIS ALERT\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n';}</script>

It would be great if I could disable this javascript code, just like I can with window move/resize, raise/lower, hide statusbar, etc..

All Replies (5)

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I have the same problem. This script attaches to random web pages, then will not allow me to close the page. I have to use Task Manager to kill Firefox.

window.onbeforeunload=function(){return 'PRESS ESCAPE OR CLOSE THIS ALERT\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\

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Same reply as above.

Modified by jhathaway

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You can either disable JavaScript temporarily (Tools > Options > Content) or use a bookmarklet like this:

javascript:void(window.onbeforeunload=null);
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The only solution I've found that works correctly cross-browser is javascript:window.onbeforeunload=null;

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First, install GreaseMonkey: https://addons.mozilla.org/en-US/firefox/addon/greasemonkey/

Then, create a new user script for all pages, or for the specific website; the script itself is very simple, it's just this line:

window.onbeforeunload=null;


It's just overriding the annoying function called at the time the page is closed, with an empty function. That's all. In some cases, it may not work if some script inside the page is modifying the DOM after the page is loaded. Have fun!