js压缩

http://dean.edwards.name/packer/

在线压缩

JSMIN, the Dojo compressor and Dean Edwards' Packer. Each

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http://developer.yahoo.com/yui/compressor/

yuiCompress很不错

Yahoo! UI Library: YUI Compressor

According to Yahoo!'s Exceptional Performance Team, 40% to 60% of Yahoo!'s users have an empty cache experience and about 20% of all page views are done with an empty cache (see this article by Tenni Theurer on the YUIBlog for more information on browser cache usage). This fact outlines the importance of keeping web pages as lightweight as possible. Improving the engineering design of a page or a web application usually yields the biggest savings and that should always be a primary strategy. With the right design in place, there are many secondary strategies for improving performance such as minification of the code, HTTP compression, using CSS sprites, etc.

In terms of code minification, the most widely used tools to minify JavaScript code are Douglas Crockford's JSMIN, the Dojo compressor and Dean Edwards' Packer. Each of these tools, however, has drawbacks. JSMIN, for example, does not yield optimal savings (due to its simple algorithm, it must leave many line feed characters in the code in order not to introduce any new bugs).

The goal of JavaScript and CSS minification is always to preserve the operational qualities of the code while reducing its overall byte footprint (both in raw terms and after gzipping, as most JavaScript and CSS served from production web servers is gzipped as part of the HTTP protocol). The YUI Compressor is JavaScript minifier designed to be 100% safe and yield a higher compression ratio than most other tools. Tests on the YUI Library have shown savings of over 20% compared to JSMin (becoming 10% after HTTP compression). Starting with version 2.0, the YUI Compressor is also able to compress CSS files by using a port of Isaac Schlueter's regular-expression-based CSS minifier.