How to hunt down HTTP request?

Trying to optimize one web project.

It uses asp.net (webforms), bunch of jquery plugins and whatnot.

Problem: there's unnecessary HTTP request to localhost/undefined and that makes every request take ~1s longer than needed.

Question: is there any tactic to find guilty code?

Clue: undefined makes me think that there's JS involved.

Firebug log:

GET /undefined HTTP/1.1

Host: localhost:17817

User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; lv; rv:1.9.2) Gecko/20100115

Firefox/3.6

Accept: image/png,image/;q=0.8,/;q=0.5

Accept-Language: lv,en-us;q=0.7,en;q=0.3

Accept-Encoding: gzip,deflate

Accept-Charset: ISO-8859-13,utf-8;q=0.7,;q=0.7

Keep-Alive: 115

Connection: keep-alive

Referer: http://localhost:17817/Default.aspx

if you right click a line in the code, it gives you a conditional breakpoint. Check the name of the variable that has the URL value, and set a condition when typeof URL === 'undefined' or url === 'undefined' and look at the stack

Just set breakproint at line 3400 (with no conditions). It does not go through there.

3397 ajax: function( s ) {

3398 // Extend the settings, but re-extend 's' so that it can be

3399 // checked again later (in the test suite, specifically)

3400 s = jQuery.extend(true, s, jQuery.extend(true, {}, jQuery.ajaxSettings, s));

Narrowed issue down a bit => commented out 1 ascx controller that renders some images and uses gallerific jquery plugin and m开发者_开发技巧agic request dissapeared.

Problem was with galleriffic plugin initialization. It couldn't find anchor and it's href for creating thumbnails when there were no images or something. It's cool now...

Have you been able to identify what JS code is initiating the request? If you are using Firebug it should give you a line of code in the console window which is invoking the AJAX request. In the event it's something like a $.post() with a code line in the jQuery library, you can navigate the callstack within the Firebug plugin to try and figure out where the initial JS call is being invoked.

You might want to try out the HTTP Watch.