ES5的常量写法

箭头函数 this指向

let Fn = function(){
   this.a = 'a';
   this.b = 'b';
   this.c = {
       a:'a+',
       b:() => this.a,
       c:() => this.c.a
   }
}
console.log(new Fn().c.b()) //a
console.log(new Fn().c.c()) //a+

ES6默认参数

可变参数

合并数组