Ray :

Recently, I've been studying ways of reducing the download size of Javascript applications produced by Google Web Toolkit, while preserving or improving startup time. There are a number of ways to do this, the first of which is to transform Javascript code into a form that is naturally more succinct, while eliminating unused code, or deferring the load of some code until later.

...

Instead, I was drawn to a reversible transform the browser already includes support for: gzip compression, and decided to ask the question: what effect does the large-scale structure of the JS output code have on the DEFLATE algorithm of GZIP which is used to serve up compressed script? The answer it turns out, is substantial.

Ray is really impressive.

On Reducing the Size of Compressed Javascript (by up to 20%)