var man = 'Tony';

function family1(){
    family2();
    console.log('你好' + man);//Tony
    function family2(){
        var man = 'John';
        console.log('你好' + man);//John
    }
}
family1();

一開始執行family1函式、再執行family2，當family2裡面需告一個man變數，其值為John且輸出結果會是John，但是family1本身沒有宣告任何man變數，所以結果會是去尋找外層的Tony

參考文獻:

• JavaScript 核心篇 (opens new window)

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