Because it's no longer the same language. You're not programming in JavaScript, you're programming in TypeScript, which happens to be compiled to something JavaScript engines accept. All the praise towards TypeScript does not necessarily apply to JavaScript. It would be like praising Assembly while you're actually programming in C.

AFAIK, the only difference between TS and JS is types. TS doesn't give you anything that's functionally different than JS -- only types that are stripped during compilation. You can't perform any logic on types at all (e.g. you can't have conditional logic based on interfaces).

Comparing assembly/C to JS/TS doesn't make sense.

Yeah, and the only difference between C and machine code is that C hasn't been compiled yet. The comparison makes perfect sense.

Writing TypeScript is like writing JavaScript but with type annotations. Writing C is not like writing assembly with type annotations.

> Writing TypeScript is like writing JavaScript but...

...but different.

> Writing C is not like writing assembly...

...it's different.

With most things, yes, if the implementation for that feature supports your operating system, and it doesn't take long enough to be noticeable, and there's no weird caching issues at any given level, then yes, it's transparent in that case.

Or you could just write the JS directly and be done with it.