How to edit JavaScript in Firebug?

_{(source: fidelitydesign.net)}

You can use the Firebug Console tab to write Javascript. I use this quite a lot of rapid prototyping of code before I integrate it into my projects. When you use the Console, javascript is executed in the context of the current page. Therefore, and scripts that are currently defined for that page, can potentionally be redefind. E.g., in the Console window, I could do this:

$ = function() { alert("Whoops"); }

...and that would redefine the $ function used by JQuery.

There is a "Scratchpad" built into the Mozilla framework. This can be reached from within Firefox.

In the "Tools" menu under "Web Developer"->"Scratchpad".

Or...

Just right click on any element on your page. Select "inspect element" On the inspector toolbar, far to the right, there is a noteblock "Scratchpad", press it.

Now you get a Javascript editor with syntax highlightning etc.. From here you can open/save your javascript source file.

Read more bout it here.