JS has atomics and shared memory arrays which also basically bypass garbage collection [1]
JS had working simd.js implementations in both Firefox and Chrome until they were pulled in favor of WASM
[0] https://v8.dev/blog/code-caching-for-devs
[1] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...
[2] https://github.com/tc39/ecmascript_simd
https://blog.mozilla.org/javascript/2015/03/10/state-of-simd...
https://01.org/blogs/2014/bringing-simd-javascript