Emacs users may wish to check out this hack (reload browser via MozRepl on save): <a href="http://hyperstruct.net/projects/mozrepl/emacs-integration" rel="nofollow">http://hyperstruct.net/projects/mozrepl/emacs-integration</a><p>It's quite neat, but very easy to get confused: if you switch to a different tab to read documentation for example, then make an edit and save, it will try and load into the new tab (usually with strange results!)
This idea isn't new. I used something just like this (but more ghetto) whenever I worked on Firefox extensions. It was called the Extension Developer Extension:<p><a href="http://ted.mielczarek.org/code/mozilla/extensiondev/" rel="nofollow">http://ted.mielczarek.org/code/mozilla/extensiondev/</a><p>It had other features, but the REPL was the most important to me. This looks much nicer though.
I'm pretty sure ChromeBug (<a href="http://getfirebug.com/releases/#chromebug" rel="nofollow">http://getfirebug.com/releases/#chromebug</a>) lets you do this, though it has some trade-offs.<p>On one hand, it's built on top of Firebug; this adds a lot of power (chrome inspection, javascript debugging/breakpoints in the chrome).<p>On the other, it's alpha, and not the focus of development (as far as I can tell)--it hasn't had a new release in some time.
<a href="http://www.croczilla.com/bits_and_pieces/jssh/" rel="nofollow">http://www.croczilla.com/bits_and_pieces/jssh/</a><p>Edit: Just realised that this is pure javascript, making it a lot easier to deploy than jssh, and also a lot more extensible. That is awesome.