Firebug 1.0 is an increasingly popular choice for debugging and inspecting Ajax applications. In addition, Firebug can also serve as a way to tweak CSS and Web page layout. Firebug creator Joe Hewitt recently gave a presentation to a group of Yahoo developers, and the video of Hewitt's talk is now available from Yahoo's YUI Theater site.

In blogging about the talk, Yahoo's Lauren Garcia commented that:

The best new thing about Firebug I've found since I've been playing with 1.0 is the expansion of Javascript logging toys. Once you get going you'll see a new tab next to the Inspect tool called "Profile" which you can turn on while you're using a page that is executing some JS, and it will record all kinds of useful info about whatever JS functions were executed between when you first hit it to start recording and when you hit it again to stop recording.

It tells you how many calls were made to each particular function as well as how much time it took and how much time it took relative to the other functions that also fired. The best part is that you can also turn the profiler on and off directly in your code just like a console.log or console.info...

This is a great leap forward for developers who are very performance-conscious about their apps, which in theory should be all of us. Another whizzbang logging feature is console.trace(), which does a stack trace of all the functions being called at the particular moment that you invoke it and traces the values being passed around to each of them.

What are your favorite JavaScript/Ajax debugging tools?