function Box(name,age){

    this.name = name;

    this.age = age;

    this.family = ['哥哥',‘姐姐’,‘妹妹’]；

 }

 Box.prototype = {

    constructor:Box,

    run:functiong(){

    return this.name+this.age+"运行中"

   }

 }

 var box1 = new Box("Lee",100);

 var box2 = new Box("Jack",200);

 function Box(name,age){

    this.name = name;

    this.age = age;

   this.family = ['哥哥',‘姐姐’,‘妹妹’]；

   if(typeof this.run !="function"){          //判断this.run是否存在

        Box.prototype.run=function(){

           return this.name+this.age+"运行中"

  }

  }

  }

 //原型的初始化只要第一次初始化就可以了，没必要每次构造函数实例化的时候都初始化。

  var box1 = new Box("Lee",100)

  var box2 = new Box("Jack",200)