typescript arrow function as parameter type code example

Example 1: generic arrow function typescript

const foo = <T extends unknown>(x: T) => x;

Example 2: typescript arrow function

let sum = (x: number, y: number): number => {
    return x + y;
}

sum(10, 20); //returns 30

Example 3: typescript pass a function as an argunetn

class Foo {
    save(callback: (n: number) => any) : void {
        callback(42);
    }
}
var foo = new Foo();

var strCallback = (result: string) : void => {
    alert(result);
}
var numCallback = (result: number) : void => {
    alert(result.toString());
}

foo.save(strCallback); // not OK
foo.save(numCallback); // OK

Example 4: arrow function in ts

// ES6: With arrow function  
var getResult = (username: string, points: number): string => {  
  return `${ username } scored ${ points } points!`;  
};

getResult('joyous jackal' , 100);