When it comes to JavaScript rendering, Apple's Safari 4 browser is almost neck-and-neck with Google's Chrome.

According to PC Advisor's sister title Computerworld, which ran JavaScript rendering tests on a number of browsers, the public beta of Safari 4 is in a virtual dead heat with the most recent edition of Google's Chrome.

However, it is 38 percent faster than the newest version of Mozilla Firefox, more than three times faster than the production edition of that open-source browser, and over five times faster than Microsoft's Internet Explorer 8.

The SunSpider JavaScript benchmark suite was run three times in Windows XP for each browser, then an average score was obtained.

Apple Safari 4 review

Mozilla Firefox 3.1 beta 2 review

Microsoft Internet Explorer 8 review

Google Chrome review

Safari 4 is almost neck-and-neck with Google Chrome when it comes to JavaScript rendering

Safari 4, which was made available this week, scored just slightly higher than Chrome, a developer-only build of Google's browser that was issued only last week. The difference, however, was tiny: Google was only about 7 percent faster.

Although Chrome and Safari are both built around the same open-source WebKit engine, they use different JavaScript engines. The former features Google's own V8 engine, while Safari 4 relies on Apple's new Nitro.

That new engine was most in evidence when Safari 4's scores are compared to those of Safari 3.2.2, the current shipping version on Windows. The beta of Safari 4 was about 3.7 times faster.

Safari 4 easily beat Firefox 3.0.6, Mozilla's production browser, and IE8 Release Candidate 1 (RC1), Microsoft's latest public release of its still-under-construction successor to the three-year-old IE7. According to SunSpider's tests, Safari 4 is nearly 3.5 times faster than Firefox and about 5.6 times faster than IE8.

When IE7 is brought into the picture, Safari 4 looks lightning-quick: Apple's browser is more than 76 times faster at completing the JavaScript tests than Microsoft's.

Most browser makers have been aggressively promoting improved JavaScript performance for months. Google, for example, bragged up Chrome's when it debuted the browser last September, while Mozilla has been talking up Firefox 3.1's TraceMonkey engine since August.

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Microsoft, however, has disparaged the benchmark bragging as a "browser drag race" that it's not interested in joining. Instead, senior product manager James Pratt has tried to steer the conversation away from JavaScript and toward a more subjective interpretation.

We're at the point, with what people do in the browser, that users can't really tell the difference between browsers," he has argued.

"Beyond building a performance lab, which we've done, it's very difficult to tell which browser is fastest. The reality is that for most users, they'll all be comparable."

On the Mac, where Safari doesn't have to compete with Google - Chrome has yet to be ported to Apple's operating system - the beta of version 4 is almost twice as fast as Firefox 3.1 Beta 2 and nearly four times faster than Firefox 3.0.6, according to SunSpider tests run on a 2.4GHz 'unibody' MacBook.

See also: Mozilla slams Microsoft for browser speed disinterest