var a = {
       name: 'li',
       say: (word) => {
           console.log(this)
           console.log(word)
       }
   }
  a.say('hi')
這個是window

var a = {
       name: 'li',
       say: function(word){
           console.log(this)
           console.log(word)
       }
   }
  a.say('hi')
這個是a對象本身

http://blog.csdn.net/liwusen/article/details/70257837 一點沒說清
http://blog.csdn.net/u013344815/article/details/73184928 最后的兩句總結(jié)和廢話差不多