I wish they had at east posted a browser-runnable version of their test so we could see for ourselves which browser is which, or compare JS vs WASM on our own systems. (On this type of code, I'd expect Safari to be the fastest, not Chrome.)
See my "minimal" C++ translation in my other post here. There's not much to add. For JavaScript start with their code, but add the allocation, just replace allocations with
var a = new Uint32Array(height * width); and b the same. Add the timing (1), put in HTML and you're done. It's easy, just a few minutes for anybody who works with that (and this site should be filled with the competent developers AFAIK).
