[qbane]

JavaScript is inherently untyped. Either the programmer tries to be very careful to make it type safe, or someone invents a programming language that can only compile to a sound subset of it. TS heads for the latter way. But things quickly go out of control when you introduce dependencies, and even a dependency without interface file can pollute your codebase with "any". I do not think TS would be mainstream if there were not many packages on npm that had included a type definition. On the other hand, a type checker/inferencer that "does less things" like Jedi has proved great success in Python community.