I mean, Dart offers this. The difference between Dart and the other strongly typed options is that a massive pile of funding (and production apps) drive Dart and its direction. So it’s quite stable, if a little too risk averse.

That said, I’ve never found Strong Typing to be that essential for front end dev. TypeScript is incredibly pragmatic, which is why it’s been so successful imo.

Nothing stops people from writing all their dependencies in TypeScript. But it’s not necessary to use it successfully.