James - 2011-06-15

https://developer.mozilla.org/en/SpiderMonkey

From the website:

SpiderMonkey is Mozilla's JavaScript engine written in C/C++. It is used in various Mozilla products, including Firefox, and is available under MPL/GPL/LGPL tri-license.

The most recent standalone source code release implements JavaScript 1.8.5, and is largely the same engine that shipped with Firefox 4. To find out more about this version of SpiderMonkey, check out the Release Notes. You can download full source code here: http://ftp.mozilla.org/pub/mozilla.org/js/js185-1.0.0.tar.gz

There are other options to SpiderMonkey, but they should not be necessary:

https://wiki.mozilla.org/JavaScript:TraceMonkey

About TraceMonkey

TraceMonkey adds native‐code compilation to Mozilla’s JavaScript® engine (known as “SpiderMonkey”). It is based on a technique developed at UC Irvine called “trace trees”, and building on code and ideas shared with the Tamarin Tracing project. The net result is a massive speed increase both in the browser chrome and Web‐page content.

And this:

https://wiki.mozilla.org/JaegerMonkey

JaegerMonkey (or JägerMonkey) is a new method JIT for SpiderMonkey. The goal is to get reliable baseline performance on the order of other JS JIT systems. JM will be a baseline whole-method JIT that doesn't necessarily do many traditional compiler optimizations. Instead, it does dynamic-language-JIT-oriented optimizations like PICs and specialization of constant operands.