看如下對象定義：
'use strict'var jane = { name ： ‘Jane', display : function(){ retrun 'Person named ' + this.name; }};這樣能正常調用
jane.display();
下面的調用會出錯：
var func = jane.display;func()
TypeError: Cannot read property 'name' of undefined
因為，this指向已經改變，正確的方式如下：
var func2 = jane.display.bind(jane);func2()
'Penson named Jane'
所有函數都有其特殊的this變量，如下面的forEach
var jane = { name : 'Jane', friends: ['Tarzan', 'Cheeta'], sayHiToFriends: function(){ 'use strict'; this.friends.forEach(function(friend) { // 'this' is undefined here console.log(this.name + ' says hi to '+ friend); }); }} 調用sayHiToFriends會產生一個錯誤：
jane.sayHiToFriends()
TypeError: Cannot read property 'name' of undefined
解決方案一：將this保存在不同的變量中
var jane = { name : 'Jane', friends: ['Tarzan', 'Cheeta'], sayHiToFriends: function(){ 'use strict'; var that = this; this.friends.forEach(function(friend) { console.log(that.name + ' says hi to '+ friend); }); }} 解決方案二：利用forEach的第二個參數，它可以給this指定一個值
var jane = { name : 'Jane', friends: ['Tarzan', 'Cheeta'], sayHiToFriends: function(){ 'use strict'; this.friends.forEach(function(friend) { console.log(this.name + ' says hi to '+ friend); }, this); }} 新聞熱點
疑難解答
