// 父类
var Super = function(name) {
    this.name = name;
    this.friends = ["lily", "meimei"];
};

Super.prototype.sayName = function() {
    console.log(this.name);
};

// 子类
var Sub = function(name, age) {

    // 属性归到属性
    Super.call(this, name);
    this.age = age;
};

// 原型归到原型
Sub.prototype = Super.prototype;

// 明确构造器
Sub.prototype.constructor = Sub;

Sub.prototype.sayAge = function() {
    console.log(this.age);
};


var sup1 = new Super("lucy", 18);
var sub1 = new Sub("lily", 20); 

sub1.friends.push("poly");

var sub2 = new Sub("poly", 2);