Function overloading OOP

// overload declaration
function sum(a: number, b: number): number;
function sum(a: string, b: number): number;
function sum(a: number, b: string): number;
function sum(a: string, b: string): number;

// overload definiton
function sum(a,b){
	if(typeof a === "string"){
		a = parseInt(a,10);
	}
	if(typeof b === "string"){
		b = parseInt(b,10);
	}
	return a + b; // add to string (after parseInt them)
}
sum(1,2);
sum("1","2"); // send 2 strings