typescript overloading code example

Example 1: typescript default parameter

// Default Parameters
sayHello(hello: string = 'hello') { 
    console.log(hello); 
}

sayHello(); // Prints 'hello'

sayHello('world'); // Prints 'world'

Example 2: how to make a parameter optional in typescript

// Optional parameter
function foo(x?: number) {
    console.log("x : "+ x);
}
foo();
foo(6);

Example 3: function overload in ts

Overloaded Funcitons:
	Set of different functions which have same name.

type Both = string | number;

function add(a: number, b: number): number;
function add(a: string, b: string): string;
function add(a: Both, b: Both) {
  if (typeof a === 'string' || typeof b === 'string') {
    return a.toString() + b.toString();
  }
  return a + b;
}

const res = add('Joyous ', '21');
console.log(res);