There is work going on in enabling Javascript to get better at doing things in parallel - both on CPU and GPU. Eg. check out the ParallelArray() from the River

There is work going on in enabling Javascript to get better at doing things in parallel - both on CPU and GPU. Eg. check out the ParallelArray() from the River Trail project by Intel: http://wiki.ecmascript.org/doku.php?id=strawman:data_parallelism http://wiki.ecmascript.org/doku.php?id=strawman:data_paralle... & http://en.m.wikipedia.org/wiki/River_Trail_(JavaScript_engine) http://en.m.wikipedia.org/wiki/River_Trail_(JavaScript_engin... At least Firefox has an initial implementation: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/ParallelArray https://developer.mozilla.org/en-US/docs/JavaScript/Referenc... The benefit if asm.js being based on ordinary javascript is that they can use these improvements to javascript itself right away more or less.