void as a type of an argument of a generic function in TypeScript

Question

It is possible to specify void as a type parameter for generic function in TypeScript. And it works fine for return values of functions. However when void

Answer 1

A useful use for void is when you want to make a parameter optional. Angular uses this a lot with RxJS Subject when emitting events and there's no useful type for the event.

The signature for Subject's next function is :

next(value?: T)

You can create a Subject which makes the value parameter forbidden:

new Subject().next() // ok

new Subject().next(true) // not allowed

as opposed to non-void where you get

new Subject().next(true)

Not sure exactly which TS version this became possible.