function expression in typescript code example

Example 1: typescript arrow function

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

sum(10, 20); //returns 30

Example 2: arrow function in ts

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

getResult('joyous jackal' , 100);

Example 3: typescript function type

// define your parameter's type inside the parenthesis
// define your return type after the parenthesis

function sayHello(name: string): string  {
  console.log(`Hello, ${name}`!);
}

sayHello('Bob'); // Hello, Bob!

Example 4: types function typescript

interface Alternate_Syntax_4_Advanced {
    title: string;
    callback<T extends unknown[], R = unknown>(...args?: T): R;
}