Issue with xhr.js

[Sabran]

I’m trying to use the latest version of jQuery and the latest version of jquery.signalR. I’m running into a problem in IE9 specifically. On window.unload, signalR is firing off an AJAX request. This fails in jquery with the error: Unable to set value of the property 'x': object is null or undefined. The ‘x’ is actually a number, but it varies.

I’ve traced the issue down to line 104 in xhr.js:

callback = xhrCallbacks[( id = xhrId++ )] = callback("abort");

The problem is that xhrCallbacks is undefined at the time of this call. The reason it is undefined is because earlier, on line 32, it is explicitly set to undefined on the window.unload event.

[Sabran]

Since this is a problem related to window.unload being called, I don't think it's reproducible using jsFiddle. Sorry.

[gibson042]

Replying to Sabran:

Since this is a problem related to window.unload being called, I don't think it's reproducible using jsFiddle. Sorry.

I recommend a reduced test case that either manually triggers "unload" or leverages iframes.

[Sabran]

Ok. Here's the jsFiddle which manually triggers unload:

​http://jsfiddle.net/wE3YU/3/

Thanks!

[Sabran]

Just a reminder, I'm only able to reproduce the error in IE9. It seems to work fine in Chrome and Firefox.

[Sabran]

Is there anything else needed from me to verify that this is a legitimate issue with jQuery?

[gibson042]

No; that'll do. Thanks!

[anonymous]

Any ETA on when this might get prioritized?

[Richard Gibson]

Fix #14379: AJAX requests on unload

Changeset: f9d41ac641dcb5a93ba8a9027476b160d8f41111