PackR

Description

PackR is a Ruby version of Dean Edwards’ JavaScript compressor.

Features

Whitespace and comment removal
Compression of local variable names
Compression and obfuscation of ‘private’ (_underscored) identifiers
Base-62 encoding

Synopsis

To call from within a Ruby program:

require 'packr'

code = File.read('my_script.js')
compressed = Packr.pack(code)
File.open('my_script.min.js', 'wb') { |f| f.write(compressed) }

This method takes a number of options to control compression, for example:

compressed = Packr.pack(code, :shrink_vars => true, :base62 => true)

The full list of available options is:

:shrink_vars – set to true to compress local variable names
:private – set to true to obfuscate ‘private’ identifiers, i.e. names beginning with a single underscore
:base62 – encode the program using base 62
:protect – an array of variable names to protect from compression, e.g.

compressed = Packr.pack(code, :shrink_vars => true,
```
:protect => %w[$super self])
```

To call from the command line (use packr --help to see available options):

packr my_script.js > my_script.min.js

Notes

This program is not a JavaScript parser, and rewrites your files using regular expressions. Be sure to include semicolons and braces everywhere they are required so that your program will work correctly when packed down to a single line.

By far the most efficient way to serve JavaScript over the web is to use PackR with the –shrink-vars flag, combined with gzip compression. If you don’t have access to your server config to set up mod_deflate, you can generate gzip files using (on Unix-like systems):

packr -s my-file.js | gzip > my-file.js.gz

You can then get Apache to serve the files by putting this in your .htaccess file:

AddEncoding gzip .gz
RewriteCond %{HTTP:Accept-encoding} gzip
RewriteCond %{HTTP_USER_AGENT} !Safari
RewriteCond %{REQUEST_FILENAME}.gz -f
RewriteRule ^(.*)$ $1.gz [QSA,L]

If you really cannot serve gzip files, use the –base62 option to further compress your code. This mode is at its best when compressing large files with many repeated tokens.

The –private option can be used to stop other programs calling private methods in your code by renaming anything beginning with a single underscore. Beware that you should not use this if the generated file contains ‘private’ methods that need to be accessible by other files. Also know that all the files that access any particular private method must be compressed together so they all get the same rewritten name for the private method.

License

(The MIT License)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the ‘Software’), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED ‘AS IS’, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.