ajaxStart and ajaxStop no longer gets fired if error in ajax success/error callbacks

[bautista.miguel@…]

In our application, we have a global loading animation which blocks during ajax requests. However, if there is a javascript exception in the ajax success/error callbacks, the animation no longer gets triggered.

I wrote a test case to illustrate the problem. ​http://jsfiddle.net/QwYpD/4/

Thanks, Miguel

[jaubourg]

You should handle exceptions in your callbacks. jQuery will halt whenever an unhandled exception bubbles up which makes it much easier to spot bugs in applications.

You could also use a prefilter rather than ajaxStart and ajaxStop:

$.ajaxPrefilter(function( options, _, jqXHR ) {
    startAnimation();
    jqXHR.always( stopAnimation );
});

[anonymous]

We always stop animation, but why is it that the global ajax start/stop no longer get fired after an exception? Shouldn't they continue to work afterwards on subsequent calls?

[jaubourg]

It's because we have a global counter that is not properly reset to 0 because the exception bubbled. One of the reasons why I always tell people to prefer prefilters whenever applicable. ajaxStart and ajaxStop take concurrent requests into account, a feature that is actually rarely useful and can easily be handled by a prefilter using a simple counter.

You could try and reset jQuery.active to 0 but I'm not sure that's a road you want to get down to.