重載

函數(shù)重載示例：

let 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 {
    // Check to see if we're working with an object/array
    // if so, they gave us the deck and we'll pick the card
    if (typeof x == "object") {
        let pickedCard = Math.floor(Math.random() * x.length);
        return pickedCard;
    }
    // Otherwise just let them pick the card
    else if (typeof x == "number") {
        let pickedSuit = Math.floor(x / 13);
        return { suit: suits[pickedSuit], card: x % 13 };
    }
}

編譯器會(huì)查找重載列表，嘗試使用第一個(gè)匹配的定義。 因此，在定義重載的時(shí)候，一定要把最精確的定義放在最前面。

注意，function pickCard(x): any 并不是重載列表的一部分，因此這里只有兩個(gè)重載：一個(gè)是接收對(duì)象，另一個(gè)接收數(shù)字。以其它參數(shù)調(diào)用 pickCard 會(huì)產(chǎn)生錯(cuò)誤。