JS can be pretty fast if you let it, but the problem is the fastest path is extremely unergonomic. If you always take the fastest possible path you end up more or less writing asm.js by hand, or a worse version of C that doesn't even have proper structs.
I find these userland libraries particularly effective, because you'll never leave JS land, conveniently abstracting over Workers, WebGL/WebGPU and WASM.
