Turns out this was an artefact of a Firebug bug. The Ajax request was cancelled, but Firebug continued reporting it as active. Details here.

I have long running XMLHttpRequests and I need to be able to abort them under certain circumstances.

I set up the request in a normal way:

ajax = $.getJSON(url + "?updates", function(data) { ...; });

Later on I want to abort this request, seems straightforward:

ajax.abort();

When I look in Firebug however, I see it is still running...

I console.log out the value of ajax just before I try and abort it, it confirms that its value is and XMLHttpRequest (with a readyState of 0).

Are there restrictions on how and when abort() fires on an XMLHttpRequest?

Turns out this was an artefact of a Firebug bug. The Ajax request was cancelled, but Firebug continued reporting it as active. Details here.

I have long running XMLHttpRequests and I need to be able to abort them under certain circumstances.

I set up the request in a normal way:

ajax = $.getJSON(url + "?updates", function(data) { ...; });

Later on I want to abort this request, seems straightforward:

ajax.abort();

When I look in Firebug however, I see it is still running...

I console.log out the value of ajax just before I try and abort it, it confirms that its value is and XMLHttpRequest (with a readyState of 0).

Are there restrictions on how and when abort() fires on an XMLHttpRequest?

• javascript
• jquery
• getjson

4 Answers 4

Calling abort resets the object; the onreadystatechange event handler is removed, and readyState is changed to 0 (uninitialized).

i do not think it cancels the request itself, it just ignores any response (manipulating the event handler)- but i didnt really try it out yet.

but it will deifnitely allow you to reuse the object - no matter if the browser still has some thread working with the old request.

you may take a look at the JSONP-Plugin With this Plugin you have the ability to manually abort the request. Also take a look at "a cautionary note" at IBM's Technical library:

First and foremost, there is no error handling for JSONP calls. If the dynamic script insertion works, you get called; if not, nothing happens. It just fails silently. For example, you are not able to catch a 404 error from the server. Nor can you cancel or restart the request.

Another great article on handling this is found here: http://www.bennadel./blog/1500-Catching-Timeout-Errors-With-jQuery-Powered-AJAX.htm.

I simply converted my .getJSON request to .ajax and added the timeout/error handling.

Thanks!

take a look at the jquery AJAX Queue/Cache/Abort/Block Manager, maybe this can help you to prevent you current situation.