Ready event fired multiple times if an unhandled exception occurs

[Michael Warning]

If a ready handler causes an unhandled exception then the ready list will be run twice. I'm testing with 1.4.3 in both Firefox and Safari. e.g.:

jQuery(document).ready(function() {

alert('in ready'); window.frooble();

});

This appears to happen because two callbacks are registered via addEventListener ("DOMContentLoaded" and "load"). The DOMContentLoaded handler cleans up after itself but it doesn't cleanup the load handler as well.

Alternatively, the ready list is null'd out after it is processed instead of making a copy, nulling the original, and only then walking the list.

[SlexAxton]

I don't think jQuery has any history of trying to act nicely when you throw unhandled exceptions. If you might throw an exception, wrap it in a try catch.

[[email protected]…]

I got bitten by this bug as well! Took hours to figure out the cause that $(document).ready was firing twice. Are you sure this is wontfix?

[anonymous]

We have also been bitten by this! We tracked it down to a 3rd party plugin throwing an exception. It seems unreasonable for us to have to patch each 3rd party plugin to make them all catch exceptions.

I'm not sure if wontfix is really the right approach here.

[[email protected]…]

Just wasted an hour and a half stepping through jQuery trying to work out what was going wrong, and this was it. The bug doesn't occur in 1.3.2.

This is a real regression.

[Rick Waldron]

Replying to [email protected]…:

Just wasted an hour and a half stepping through jQuery trying to work out what was going wrong, and this was it. The bug doesn't occur in 1.3.2.

This is a real regression.

Test in 1.4.4rc2

k thanks.

[Nicolas Cordin <[email protected]…>]

Hi, this is not fix in 1.4.4rc2.

I also think it's a important regression, we have really strange results when we are testing/coding applications.

I lost hours to understand what happend and finding this bug.

[Rick Waldron]

Confirmed. But still, I don't think you should hold jQuery responsible for your unhandled exceptions.

​http://jsfiddle.net/rwaldron/S2D5b/1/

[[email protected]…]

I disagree. While jQuery should not "be responsible" for the unhandled exception, it shouldn't as a side-effect create a new exception. This is exactly what is happening here. This means that I cannot trust .ready() because it may actually execute more than once...!?

This is a very undesirable bug especially when considering 3rd party code which you have little or no control over.

I agree that many problems should just be problems until fixed by users but this is a side-effect problem which is dangerous and greatly reduces trust in a much relied on and needed method from jQuery.

[[email protected]…]

I concur with buddywilliams that while jQuery shouldn't cause further problems due to already existing issues. Just ran into this myself and debugged for about an hour until I stumbled across this post.

[[email protected]…]

Nevermind, it appears to be fixed in 1.4.4. Why does the jQuery front page say the latest release is 1.4.3 =/