jQuery.ajax 'success' callback in chrome/chromium

I am using the nginx's upload progress module.

I need a JS function to GET the progress periodically.

I tried this (I changed the url path when I applied it on my server) but it does not work on chro开发者_如何转开发me/chromium 12/13. (IE 8/9 Firefox 3+ OK. IE7 not tested)

I used Firebug to add some assertion, and found that the onStateChange is never called in chrome/chromium. (that is, the readyState is never 4)

Then I tried to rewrite the code in $.ajax(). The success callback is also never called (IE8/9 Firefox 3+ OK)

However, when I write some simple small ajax function to test in chrome/chromium, it's all right...

I need some hints.

Thank you for your time.

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EDIT: When I use the function to send the ajax request manually in chrome's console, it is successful...