call,apply和bind的用法及区别

例1

 1   var name = ‘小王‘, age = 17
 2   var obj = {
 3     name: ‘小张‘,
 4     objAge: this.age,
 5     myFun: function() {
 6       console.log(this.name + ‘年龄：‘ + this.age);
 7     }
 8   }
 9 
10   console.log(obj.objAge); //17
11   obj.myFun() //  小张年龄：undefined