is easy to use
has a high compression rate
Produce reliable end results (doesn’t mess up the code)
Node.js internals). It’s a lot faster than both YUI Compressor and Google Closure, it compresses better than YUI on all scripts I tested it on, and it’s safer than Closure (knows to deal with “eval” or “with”).
Other than whitespace removal, UglifyJS also does the following:
- changes local variable names (usually to single characters)
- joins consecutive var declarations
- avoids inserting any unneeded brackets, parens and semicolons
- optimizes IFs (removes “else” when it detects that it’s not needed, transforms IFs into the &&, || or ?/: operators when possible, etc.).
- removes quotes from keys in object literals, where possible
- resolves simple expressions when this leads to smaller code (1+3*4 ==> 13)
PS: Oh, it can “beautify” as well. 😉
Revisiting this question a few years later, UglifyJS, seems to be the best option as of now.
— Old answer below—
Previous to that the various options were as follow
The tests were done on jQuery code btw.
- Original jQuery library 62,885 bytes , 19,758 bytes after gzip
- jQuery minified with JSMin 36,391 bytes , 11,541 bytes after gzip
- jQuery minified with Packer 21,557 bytes , 11,119 bytes after gzip
- jQuery minified with the YUI Compressor 31,822 bytes , 10,818 bytes after gzip
YUI Compressor is the way to go. It has a great compression rate, is well tested and is in use among many top sites, and, well, personally recommended by me.
I’ve never used its CSS compression capabilities, but they exist as well. CSS compression works just as well.
I actually have an MSBuild task in a Web Deployment Project in my current Visual Studio solution that runs a script which in turn runs all of the solution’s JS files through ShrinkSafe before we deploy and it works quite well.
EDIT: By the way, “best” is open to debate, since the criteria for “best” will vary depending on the needs of the project. Personally, I think ShrinkSafe is a good balance; for some people that think smallest size == best, it will be insufficient.
EDIT: It is worth noting that the YUI compressor also uses Rhino.
Try JSMin, got C#, Java, C and other ports and readily available too.
If you use Packer, just go far the ‘shrink variables’ option and gzip the resulting code. The base62 option is only for if your server cannot send gzipped files. Packer with ‘shrink vars’ achieves better compression the YUI, but can introduce bugs if you’ve skipped a semicolon somewhere.
base62 is basically a poor man’s gzip, which is why gzipping base62-ed code gives you bigger files than gzipping shrink-var-ed code.