Typescript - Higher order function types

Question

I'm getting really excited about TypeScript. How do you set the type of a function parameter?

function twoMoreThanYou(calculateANumber: Function):number {     return calculateANumber(4) + 2; }  function double(n:number):number {     return n*2; }  console.log("TWO MORE", twoMoreThanYou(double)) 

How can I type calculateANumber better? I'd like to specify that it must be a function that takes a number and returns a number.

Can I then make an "interface" or some shorthand for that type so I can make my higher order function signatures more readable?

Answer 1

These both work

interface NumberFunction extends Function {     (n:number):number; }  function twoMoreThanYou(calculateANumber: (n:number)=>number):number {     ... }  function twoMoreThanYou(calculateANumber: NumberFunction):number {     ... }