On November 5th, Google released Closure Compiler for Javascript optimization. The strongest part of the Closure Compiler is that it does not only remove whitespace but also rewrites Javascript Code to make it smaller. It also optimizes your Javascript code to perform better. You can find more details and all of its features on my previous article: Closure Compiler – Javascript Compiler by Google.

During my tests, Closure Compiler reduced Javascripts more than 60%. Considering, the size of Javascript files that modern websites have and the reduction before HTTP compression, Closure Compiler is really useful. 

Closure Compiler comes with a Java based command line tool and a RESTful API.  RESTful API works great and very fast. API can be used with a MSBuild or NAnt script to automatically compress Javascript files.

I wrote a C# wrapper for the Google Closure Compiler:

C# wrapper for the Google Closure Compiler

The Closure Compiler has three compilation levels:

• WHITESPACE_ONLY: just removes whitespace and comments from the Javascript
• SIMPLE_OPTIMIZATION: performs compression and optimization that does not interfere with the interaction between the compiled JavaScript and other JavaScript. This level renames only local variables.
• ADVANCED_OPTIMIZATIONS: achieves the highest level of compression by renaming symbols in your JavaScript. When using ADVANCED_OPTIMIZATIONS compilation you must perform extra steps to preserve references in other Javascript files

Below is an example of using the Google Closure Compiler C# wrapper with ASP.NET

Compress googleClosure = new Compress();
string script = googleClosure(Server.MapPath("~/script.js");

Download Closure.cs

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