Javascript interpreters and their performance are receiveing a lot of attention lately. There is a very healthy competition going between Mozilla TraceMonkey, Google V8 and now Apple is back with SquirrelFish Extreme, an improved version of the original SquirrelFish. The new version features extensive JIT optizations and a structure cache. They even went as far as including a JIT compiled regexp engine which as far as I know is completely unprecedented:

You can write the kind of text processing code you’d want to do in Perl or Python or Ruby, and do it in JavaScript instead. In fact we believe that in many cases our regular expression engine will beat the highly tuned regexp processing in those other languages.

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