Order of execution of event listeners
Say you attach several listeners to an event, for example you want a few things to happen on page load. What is the order of execution of the different listeners? You'd think that the listener attached first will execute first, followed by the second and so on… Well, yes, in FF, Opera, Safari on Windows, but not in IE.
The test
var i = 1, ol = document.getElementById('result'); for (i; i <= 10; i++) { YAHOO.util.Event.addListener(window,'load', function(num){ return function(){ ol.innerHTML += '<li>' + num + '</li>'; } }(i) ); }
Result in FF, O, Safari
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
Result in IE
- 1
- 2
- 4
- 6
- 8
- 10
- 9
- 7
- 5
- 3
Observation
Here you can try it out yourself
Try in IE. Reload. Reload again. Notice something? The order is not random. Always starts 1, 2, then goes through all even numbers until 10 then backwards - 9, 7, 5, 3 - all odd numbers.
Try with a bigger loop - still the same thing. Hmm, interesting… Maybe not something you'd like to rely on, but still…
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August 14th, 2007 at 4:40 am
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August 17th, 2007 at 8:07 am
Correction:
This appears to be a feature/bug of the YAHOO.util.event code.
If you roll your own addEventListenter function… that (for IE), calls attachEvent(…) you'll find that they are added in the "correct" order.
Cheers,
Steve
August 17th, 2007 at 3:31 pm
Really? Interesting…