From the 'Open Source Development' files:

Google builds a lot of its own tools as part of its development efforts. Sometimes we get all 'get lucky' and the tools become open source and available too.

That's what has happened today with the Google Closure tools which are a set of JavaScript optimization tools.  Considering the extreme importance of JavaScript in all modern web applications and browsers, it makes sense in my opinion for Google and everyone else to have the best JavaScript code possible.

Among the tools released by Google is the Closure Compiler which aims to compile web apps down into compact, JavaScript code.

"The compiler removes dead code, then rewrites and minimizes what's left so that it will run fast on browsers' JavaScript engines," Google stated. "The compiler also checks syntax, variable references, and types, and warns about other common JavaScript pitfalls."

That's kinda cool, but what's even more impressive in my opinion are the usage mechanisms that Google is making available for the Closure Compiler. In addition to the command-line they've also got a Firefox extension that works with their Page Speed optimization tool.

What that means to me is I can easily check JavaScript on any page and see how the JavaScript can be improved.

That's one heck of a powerful tool to have.