Typescript Function Types

I keep having to look this up again, so for all my future references…

Inline params:

class MyClass {
  myMethod(callback: (x: string) => void) : void {
    callback('hi');
  }
}

function myFunction(callback: (x: string) => void) : void {
  callback('hi');
}

As an interface

interface MyCallback {
  (x: string): void;   
}

class MyClass {
  myMethod(callback: MyCallback) : void {
    callback('hi');
  }
}

function myFunction(callback: MyCallback) : void {
  callback('hi');
}

With generics

interface Action<T> {
    (arg: T): void;
}

interface Func<T,TResult> {
    (arg: T): TResult;
}

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