But 2-3x speedup over a well written Javascript version running in a modern Javascript engine is quite impressive, isn't it?
One thing that's often overlooked is that even though "idiomatic Javascript" using lots of objects and properties is fairly slow, it can be made fast (within 2x of native code compiled from 'generic' C code) by using the same tricks as asm.js (basically, use numbers and typed arrays for everything). But the resulting Javascript code will be much less readable and maintainable than cross-platform C code that's compiled to WASM.
One thing that's often overlooked is that even though "idiomatic Javascript" using lots of objects and properties is fairly slow, it can be made fast (within 2x of native code compiled from 'generic' C code) by using the same tricks as asm.js (basically, use numbers and typed arrays for everything). But the resulting Javascript code will be much less readable and maintainable than cross-platform C code that's compiled to WASM.