'use strict'
var jane = {
  name ： ‘Jane',
  display : function(){
    retrun 'Person named ' + this.name;
  }
};

jane.display();

var func = jane.display;
func()

TypeError: Cannot read property 'name' of undefined

var func2 = jane.display.bind(jane);
func2()

'Penson named Jane'

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);
    });
  }
}  

jane.sayHiToFriends()

TypeError: Cannot read property 'name' of undefined

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);
    });
  }
} 

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);
  }
}