monline

You can check various aspects of your javascript code. The intention behind JSLint is to spot potentional coding/syntax problems in your JS code that might lead to bugs or messed up code.

Firefox has a built-in timeout for JavaScripts to prevent them from running too long. It is far from perfect (see this post for details on some possible problems), but better than nothing. You can set the timeout period in the dom.max_script_run_time preference (using the "about:config" URL), it's 10s in FF 2.x by default. You might need this if you're using lots of extensions, eg. web development stuff (Web Developer ext., Firebug, DOM Inspector, etc.). Some of these can trigger the timeout warning for web pages with larger DOMs, etc. Being a web developer, I see this warning a way too many times.

I've seen the following code in jQuery's source and various jQuery plugins, but I did not really understand what it is meant to do:

Interface is a collection of rich interface components which utilizes the lightweight JavaScript library jQuery. With this components you can build rich client web applications and interfaces with the same simplicity as writing JavaScript with jQuery.

Flot is a pure Javascript plotting library for jQuery. It produces graphical plots of arbitrary datasets on-the-fly client-side.
The focus is on simple usage (all settings are optional), attractive looks and interactive features like zooming.
Although Flot is easy to use, it is also advanced enough to be suitable for Web 2.0 data mining/business intelligence purposes which is its original application.

A large collection of DHTML JavaScript code grouped/tagged into categories.

This is a popular JavaScript compressor written by Dean Edwards. I've found it through jQuery since it is compressed/packed using Packer.

Nice tool for formatting compressed JavaScript into a readable form.

The website reports about all kinds of news in modern (call it Web 2.0 ) web development. This involves CSS, HTML, JavaScript, XML, browsers, JS libraries, web standards, etc. A good source of up to date info on RIA development.

Firebug is a superb Firefox extension providing tons of tools in a very usable structure to aid you in HTML+CSS+JavaScript development. It also has good support for logging in your JavaScript code. Now a jQuery developer can take use of this to log any jQuery object to the console.