[bastawhiz]

Performance. WebAssembly has no JIT stage, it gets AOT compiled straight to machine code. Plus, it gives (or will give) much lower-level access to features like threads and memory allocation.

[amaranth]

Thanks to Spectre I don't think we'll be seeing threads anytime soon. Well, not threads with shared memory anyway which removes a lot of the point of them. Same reason JavaScript just lost SharedArrayBuffer, too easy to make a high precision timer out of it.

[kllrnohj]

> Plus, it gives (or will give) much lower-level access to features like threads and memory allocation.

There's no reason JavaScript couldn't just have those features. It already has some amount of memory allocation control via ArrayBuffer & DataView.

[imtringued]

You're describing asm.js which had significant issues as a compilation target. The generated javascript code was massive and it took several seconds just to parse it.

[caseymarquis]

Related is a mozilla post on streaming wasm for big performance gains: https://hacks.mozilla.org/2018/01/making-webassembly-even-fa...

[kllrnohj]

asm.js never added threads, which is a far bigger performance issue than fine-grained manual memory allocation is.