This post was written by David Mandelin who works on Mozilla’s JavaScript team. Firefox 3.5 has a new JavaScript engine, TraceMonkey, that runs many JavaScript programs 3-4x faster than Firefox 3, speeding up existing web apps and enabling new ones. This article gives a peek under the hood at the major parts of TraceMonkey and how they speed up JS. This will also explain what kinds of programs get
![an overview of TraceMonkey – Mozilla Hacks - the Web developer blog](https://cdn-ak-scissors.b.st-hatena.com/image/square/8f043099b608abf8384b24171faa177d3698e62e/height=288;version=1;width=512/https%3A%2F%2Fhacks.mozilla.org%2Fwp-content%2Fthemes%2FHax%2Fimg%2Fhacks-meta-image.jpg)