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Performances of JavaScript Compressors JavaScript compression is one of most important missions to optimize the performance of web page. Besides minifying the size of JavaScript source code/files (minify JS/compress JavaScript files) to decrease the time for loading, some JavaScript compressors also make many optimizations (compress) for your JavaScript source code.

Today in this post, jsB@nk would like to show you comparison results of some popular JavaScript compressors: Packer 3.1, YUI Compressor, Google Closure, Dojo Shrinksafe and JSMin. This comparison just made with two test units: compression ratio and processing time. Please go to the full post page for detailed comparison results.


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So following on from last weeks post I have taken a closer look at the common tools used to compress JavaScript. Below is a graph of the compression ratios that these tools achieved when applied to ext-all-debug.js, the uncompressed JavaScript from the popular ExtJS framework :

Some points to note are:

  • GZip is rather different from the other forms of compression in that it a compression of the content rather than the JavaScript, and therefore can be applied to compressed JavaScript. I have included it in the graph to provide an indication of the level of compression it can provide.
  • The simple compilation option was used with Google Closure as this is typically the one that will be used. For a discussion on why, check out the excellent post on A Log of Javascript.
  • Packer is similar to GZip in that it is more a compression of the content rather than JavaScript itself. Unlike GZip however, it has a runtime cost associated with the unpacking of the JavaScript on each page load.

Below is a graph of the processing time required for the above compressions:

Aside from Packer, there is not a lot of difference, and since all of the processing is done before deployment the compression cost does not impact the performance of the JavaScript.

The final graph below shows the compression ratios where each of the compressed JavaScript files are then GZipped, as is more typical of production environments.

In the final analysis it is clear that you should GZip your JavaScript, although be aware that not all browsers correctly handle GZipped content. As to which of the other compression tools you use, it comes down to your JavaScript. My experience showed Packer to produce the best results for ext-all-debug.js whereas Julien found that the YUI Compressor is a better choice for jQuery. CompressorRater can help with this task although it does not yet include Google Closure.

JavaScript by day


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