JavaScript Obfuscator

JavaScript Obfuscator: "The features summary of JavaScript Obfuscator
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Unique! It can compress names of local variables (like YUI Compressor does) while obfuscating (or keeping the same) names of all other symbols; names of local variables can also be mangled after compressing them to get more cryptic code
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JavaScript Obfuscator has special modes that assign local variable names a shortest name possible (considering the scope of variable) like YUI Compressor does. In fact, a modified and optimized version of YUI compressor is used for such modes - thus it's very reliable and well-tested.

After local variables are assigned shortest names possible, these name assignments can be kept (while mangling all other symbols using other mangler - e.g. md5) resulting in very short output. Alternatively, the assigned names can be also mangled after that, like all other symbols - this resulting in different resulant name being assigned to variable of the same name in different scopes.

An interesting special case is when mangler 'none' (that does not alter symbol names) is used for all other symbols - all public API of your scripts is preserved (so you don't have to compose lists of exceptions and test your code extensively), while name of local variables get shortest meaningless names. The output will have much smaller size compared to size of input"

I recommend using an obfuscator like this one after using Dojo to compress it.