1. function getAge() {
    2.     var y = new Date().getFullYear();
    3.     return y - this.birth;
    4. }
    6. var xiaoming = {
    7.     name: '小明',
    8.     birth: 1990,
    9.     age: getAge
    10. };
    12. console.log(xiaoming.age()); // 25, 正常结果
    13. console.log(getAge()); // NaN 此时this指向全局变量windows
    2. 'use strict'
    3. var xiaoming = {
    4.     name: '小明',
    5.     birth: 1990,
    7.     age: function () {
    8.         var that = this;
    9.         console.log(that)
    11.         function getAgeFromBirth() {
    12.             var y = new Date().getFullYear()
    13.             return y - this.birth;
    14.         }
    16.         return getAgeFromBirth()
    17.     }
    18. }
    20. console.log(xiaoming.age()); //cannot read property birth of underfined
    22. //原因是this指针只在age方法的函数内指向xiaoming，在函数内部定义的函数，this又指向undefined了！（在非strict模式下，它重新指向全局对象window！）
    24.     修复的办法也不是没有，我们用一个that变量首先捕获this：