If TypeScript’s tools would provide hints and type inference for standard JS files by default, I’d use it instead of Tern.js and recommend that setup to everybody. Easy choice.
You Might Not Need TypeScript (or Static Types)
Eric Elliott

IIRC, Visual Studio Code can do this already. Assuming someone made a typing file, of course.

For me this is yet another reason NOT to use Typescript. Since you can get the typings without having to use it.