AjaxLine

Julien Lecomte created compression tool for JavaScript

What is the YUI Compressor?

The YUI Compressor is a new JavaScript minifier. Its level of compaction is higher than the Dojo compressor, and it is as safe as JSMin. Tests on the YUI library have shown savings of about 18% compared to JSMin and 10% compared to the Dojo compressor (these respectively become 10% and 5% after HTTP compression)

How does it work?

The YUI Compressor is written in Java (requires Java >= 1.4) and relies on Rhino to tokenize the source JavaScript file. It starts by analyzing the source JavaScript file to understand how it is structured. It then prints out the token stream, replacing all local symbols by a 1 (or 2, or 3) letter symbol wherever such a substitution is appropriate (in the face of evil features such as eval or with, the YUI Compressor takes a defensive approach by not obfuscating any of the scopes containing the evil statement). The YUI Compressor is open-source, so don’t hesitate to look at the code to understand exactly how it works.