JavaScript如何借用构造函数继承

function girlFriend(){
    this.girls = ['chen','wang','zhu'];
  }
  function Person(){
    girlFriend.call(this,20);
  }
  var wang = new Person();
  var zhu = new Person();
  wang.girls.push('zhang');
  console.log(wang.girls);  //(4) ["chen", "wang", "zhu", "zhang"]
  console.log(zhu.girls);    //(3) ["chen", "wang", "zhu"]

function SuperType(name){
    this.name = name;
  }
  function SubType(){
    SuperType.call(this,"nick");
    this.age = 20;
  }
  var instance = new SubType();
  console.log(instance.name);    //nick
  console.log(instance.age);    //20

girlFriend.prototype.sayHello = function(){
    console.log('hello');
  }