Specifically, do you worry that Microsoft is going to eventually do the Microsoft thing and horribly fuck it up for everyone? I’ve really grown to appreciate the language itself, but I’m wary of it getting too ingrained at work only to have the rug pulled out from under us when it’s become hard to back out.
Edit: not really “pulling the rug”, but, you know, doing the Microsoft classic.
No, it doesn’t fail. It compiles to perfectly valid JS that runs exactly as you’d expect. The type checking itself errors, because you’ve made an error - but the compilation isn’t prevented by this error.
So yes, Typescript is a superset of JavaScript.
Wouldn’t it fail in strict mode?
The type checking does, but not the compilation.
That is an important difference. Still lots of people, myself included, classify “compiler printing an error (not a warning)” as failure, even if bizzarly the code still runs somehow.
That’s because you’re missing the distinction between compiler and type checker. The compiler doesn’t check types, it strips them. The type checker only checks types, it doesn’t compile. They are often used in conjunction, though increasingly the compilation is done by e.g. esbuild.
But there is nothing “bizarre” about the code running, since literally, TS is a superset of JS.