With the release of Chrome by Google, the race for he fastest Javascript engine was on. Just weeks later, the Webkit team has released a new version of their own Squirrelfish engine, Squirrelfish Extreme, which is way faster than it’s predecessor:

Charles Ling adds a comparison to Chrome’s V8 engine as well:

  • WebKit SquirrelFish Extreme: 864.1 ms
  • Google V8: 1174.1 ms
  • Mozilla TraceMonkey: 1334.6 ms

The results above are for the Sunspider benchmark, the Dromaeo benchmark shows similar results. But be aware that some of the speed improvements are only for the most common cases:

One of the things we did was to optimize within opcodes. Many JavaScript operations are highly polymorphic – they have different behavior in lots of different cases. Just by checking for the most common and fastest cases first, you can speed up JavaScript programs quite a bit. 

So if your particular application uses some uncommon operations it might be a bit slower. The JIT compiler also has some x86 32-bit only optimizations, but I expect these will be ported to other architectures soon.