function add(x: string, y: string): string;
function add(x: number, y: number): number {
	return x + y;
}
 
add(’1’,’2’);

function add(x: string, y: string): string;
function add(x: number, y: number): number;
function add(x: number | string, y: number | string): number | string {
  if ((typeof x === "number") & (typeof y === "number")) {
    return x + y;
  } else if ((typeof x === "string") & (typeof y === "string")) {
    return x + y;
  } else {
    throw new Error("Invalid types of arguments");
  }
}
 
add("1", "2");