[jws]

Browsing the alternatives in the shootout dataset, LuaJIT appears to be the fastest of the dynamic languages and feature-wise matches Javascript well enough to be a fair benchmark.

You can gain another factor of 2 or so in speed by going to a static language like C or Ada, but that isn't really a fair comparison and you can see the price paid in code size.

The good news for the web is that there may be another factor of 2 to 3 available for Javascript speedup.

[eru]

You can also go to a static language like OCaml. They don't blow up your code size, but are also fast.