The Mozilla Foundation is working on a new Javascript compiler called Tracemonkey, writes Mike Shaver on his blog. This so-called jit compiler has shown it can parse Javascript up to forty (40) times faster that its predecessor.

To get to this massive improvement, Tracemonkey uses a technique called tracing. This means that collections of Javascript code are analyzed, summarized and memorized. The next time a script contains similar code, Tracemonkey falls back to the memorized code and uses that instead, resulting in a speed improvement of up to one fortieth of the original execution time.

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