These languages are not used by virtually all JS programmers. Babel and TS is.
The other issues you mention are solved by using ESLint which flags code like this.
I do not encounter these issues in my life as a professional JS programmer, neither do my colleagues; and I'm not on my first project, don't worry. For all practical purposes they are non-existent.
anyways, we are all happy for wasm, it's not that we love JS so much.
