Typescript function overloading

pickcard.ts

var suits = ["hearts", "spades", "clubs", "diamonds"];

function pickCard(x: {suit: string; card: number; }[]): number;
function pickCard(x: number): {suit: string; card: number; };
function pickCard(x): any {

  if (typeof x == "object") {
    var pickedCard = Math.floor(Math.random() * x.length);
    //return pickedCard;
	return 'notANumber';
  }

  else if (typeof x == "number") {
    var pickedSuit = Math.floor(x / 13);
    return { suit: suits[pickedSuit], card: x % 13 }; 
  }
}

var myDeck = [{ suit: "diamonds", card: 2 }, { suit: "spades", card: 10 }, { suit: "hearts", card: 4 }];

var a: number = pickCard(myDeck);
alert(a);