Using JavaScript or jQuery how to check if event exists on the window?

Question

I've attached an event to the 'window' object, and I would like to check that it's there via code.

window.addEventListener('beforeunload', function(e){ /*...*/ }, false)

I've tried the simple, and jQuery, without luck. I have more attempts up on jsFiddle.

window.beforeunload //is undefined as is window.onbeforeunload

$(window).data('events') //not working either

Is this possible?

There are similar questions (here and here) about the DOM, and other elements, but none of the approaches in those that I have tried have worked.

score 10 · Accepted Answer · answered Feb 14 '12 at 01:39

10

You can use the in operator...

'onbeforeunload' in window;  // true (if supported)

If supported, the property will exist, though the value will be null.

answered Feb 14 '12 at 01:39

Thanks. Works in IE, Chrome, but not FF. – Nick Josevski Feb 14 '12 at 01:52
@NickJosevski: Works for me in FF 10. When you say it doesn't work, what do you mean? What result are you getting? – Feb 14 '12 at 01:56
Oh that's right, tested in FF 3.6... Works in 10. Thanks :) Problem still in Opera 11.61 but I can live with that. – Nick Josevski Feb 14 '12 at 02:02

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