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