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Debugging Ajax code with Firebug

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I've a couple of problems debugging code returned in an Ajax call - specifically, a function returned in json (errors don't get trapped in Firefox) - up to the point where I started debugging these problems in Internet Explorer (I think it's a firefox related problem, as Venkman doesn't detects those errors either) Do you know of any way to debug code returned in json from an Ajax call?


EDITED 03/04/2009 15:05


Thanks to all for your responses, but I think I didn't explain myself well enough. I know enough of Firebug to do basic debugging, but my problem happens when I fetch some code in an Ajax call that has a problem with it. Let's say we have the following HTML file (you'll need prototype in the same folder to make it work correctly):

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"     "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <script type="text/javascript" src="prototype.js"></script> </head> <body> <script> function ajaxErrorTest() {     new Ajax.Request('data.json', {            'method': 'get',            'onSuccess': function(data){            if(data.responseJSON.func)            data.responseJSON.func();}}); } </script> <input type="button" value="test" onclick="ajaxErrorTest();" /> </body> </html> 

and then, the contents of the data.json file is this:

{'func':function(){console.log('loaded...');alert('hey');}} 

If you load the page in a browser and click the 'Test' button (and everything goes well) you'll get something in the console, and an alert box that says 'hey'. Now change the data.json file to this:

{'func':function(){console.log('loaded...');alerts('hey');}} 

...and click the 'Test' button again (no need to reload the page ;-) You get the console line, but no alert box... and no errors!!! this is the kind of errors I'm trying to debug.

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Erico Lendzian Avatar asked Mar 03 '09 15:03

Erico Lendzian


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What is firebug debugging tool?

The Firebug tool lets developers inspect, edit, and debug code in the Firefox browser as well as monitor CSS, HTML, and JavaScript in webpages.


1 Answers

Try clicking on the "Console" panel (it's a tab) and enabling it. You will find that any HTTP requests will be caught along with any information that they contain. I use this in order to view any JSON stored in the request as well as any errors (500/404/etc).

Also be aware that you have to enable the console panel on a per-domain basis. There are usually three subtabs: headers, post, and response. I usually use the post/response tabs quite a bit when I'm debugging my AJAX.

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Bryan A Avatar answered Sep 18 '22 14:09

Bryan A