6 replies

Help me type this function

I have a function that takes in an input function and returns another function who's input is the same type as the function passed into it.

function Foo<T>(callback: (input?: T) => void){
  return async function(input?: T) => {
    //...
  }
}

function Foo<T>(callback: (input?: T) => void){
  return async function(input?: T) => {
    //...
  }
}

However, I want the return function type to either require or not require

input

input

based on if

callback

callback

has a parameter or not. How would I do this?