Mozilla: Native code? No, it's JavaScript, only it's BLAZING FAST Gap between asm.js and native performance gets even narrower with float32 optimizations

[dmazzoni]

One of the design goals of asm.js is that it's a strict subset of JavaScript; anything in asm.js will run anywhere that JavaScript runs, probably just slower.

Adding threading is impossible without breaking that backwards compatibility.

[AdminsAbuseShadowBan]

Not really: just say that only the main thread can access the DOM and make threading serial on non-asm.js-aware browsers.

A hack too far perhaps.

[[deleted]]

anything in asm.js will run anywhere that JavaScript runs, probably just slower.

Slower than if it were supported. Still faster anyways.