TypeScript has the equivalent of what you're describing via the `Parameters` and `ReturnType` utility types [1][2], and I've found these types indispensable. So you can do the following:

  type R = ReturnType<typeof someFunction>
  type P = Parameters<typeof someFunction>

[2] https://www.typescriptlang.org/docs/handbook/utility-types.h...

Yeah, now that you mention it, I remember using it a lot when I worked more in that language.