JavaScript: Firefox catching up thanks to JägerMonkey

The Firefox web browser lately been regarded as a bit sluggish in handling JavaScript code and it's slower in this respect than almost all of its competitors. Even the beta versions of Microsoft Internet Explorer 9 are reportedly faster than Firefox. But the new JavaScript engine called JägerMonkey, which was originally announced at the beginning of 2010, is expected to change that.

The new JavaScript engine uses methods that have proven useful in other browsers and combines them with the current TraceMonkey JavaScript engine, which turns out to be better than the competition, but only when TraceMonkey can really play its main strength: tracing. If not, Firefox has to resort to the old, slow JavaScript interpreter.

To take advantage of the speed benefits of TraceMonkey, JägerMonkey compiles complete methods as machine code in such situations, even if this process is a bit slower. In return, the compiled code can be used much more often. If this strategy can be effectively implemented, Firefox could take over the competition and be back at the head of the pack.

As recent benchmarks by Mozilla developer Rob Sayre show, Mozilla may have sped up remarkably thanks to this approach by the time Firefox 4 has been released. While Internet Explorer 9 Preview 3, Webkit in the developer version from September 08, 2010, Chrome 6.0.472.55 and Opera 10.61 are all faster, the gap has shrunk considerably.

Nightly preview builds of Firefox JS running JägerMonkey are available to download from the project's site. As with all development releases, use in production environments and on mission critical systems is not advised.

See also:

• Jägermonkey: it’s in ur browser!!!, a Mozilla blog post.
• Firefox afterburner for JavaScript, a report from The H.

(crve)