组合继承

* 原型实现继承
* 借用构造函数实现继承
* 组合继承：原型继承+借用构造函数继承
* */
function Person(name,age,sex) {
    this.name=name;
    this.age=age;
    this.sex=sex;
}
Person.prototype.sayHi=function () {
    console.log("你好啊，嘻嘻嘻");
};
function Studeny(name,age,sex,score) {
    //借用构造函数：属性值重复的问题
    Person.call(this,name,age,sex,score);
    this.score=score;
}
//改变原型指向====》继承
Studeny.prototype=new Person();//不传值
Studeny.prototype.eat=function () {
    console.log("吃好吃的");
};
var stu1=new Studeny("小美",20,"女","100");
console.log(stu1.name,stu1.age,stu1.sex,stu1.score);
stu1.sayHi();
stu1.eat();
var stu2=new Studeny("小丽",22,"女","120");
console.log(stu2.name,stu2.age,stu2.sex,stu2.score);
stu1.sayHi();
stu1.eat();