JS can be largely fast enough for a lot of use cases: if I had some WebAssembly to a project I need a good reason to do so.
JS can be faster in enough cases where it's worthwhile to test.
WASM is mostly being used for code that has already been written and is now being integrated into a web site. I wouldn't suggest jumping right to WASM simply for performance.
JS can be largely fast enough for a lot of use cases: if I had some WebAssembly to a project I need a good reason to do so.