Declare a delegate type in Typescript

Question

Coming from a C# background, I want to create a datatype that defines a function signature. In C#, this is a delegate declared like this:

delegate v         


        

Answer 1

In TypeScript, interfaces can have call signatures. In your example, you could declare it like this:

interface Greeter {
    (message: string): void;
}

function sayHi(greeter: Greeter) {
    greeter('Hello!');
}

sayHi((msg) => console.log(msg)); // msg is inferred as string