<script type="text/javascript">
  /**
   * 使用约定优先的原则，把所有的私有变量都使用_开头
   */
  var Person = function (no, name, age)
  {
   this.setNo(no);
   this.setName(name);
   this.setAge(age);
  }
  Person.prototype = {
   constructor: Person,
   checkNo: function (no)
   {
    if (!no.constructor == "string" || no.length != 4)
     throw new Error("学号必须为4位");
   },
   setNo: function (no)
   {
    this.checkNo(no);
    this._no = no;
   }, 
   getNo: function ()
   {
    return this._no;
   setName: function (name)
   {
    this._name = name;
   }, 
   getName: function ()
   {
    return this._name;
   }, 
   setAge: function (age)
   {
    this._age = age;
   }, 
   getAge: function ()
   {
    return this._age;
   }, 
   toString: function ()
   {
    return "no = " + this._no + " , name = " + this._name + " , age = " + this._age;
   }
  };
  var p1 = new Person("0001", "小平果", "22");
  console.log(p1.toString());  //no = 0001 , name = 小平果 , age = 22
  p1.setNo("0003");
  console.log(p1.toString());  //no = 0003 , name = 小平果 , age = 22
  p1.no = "0004";
  p1._no = "0004";
  console.log(p1.toString()); //no = 0004 , name =小平果 , age = 22

 </script>

<script type="text/javascript">
  /**
   * 使用这种方式虽然可以严格实现封装，但是带来的问题是get和set方法都不能存储在prototype中，都是存储在对象中的
   * 这样无形中就增加了开销
   */
  var Person = function (no, name, age)
  {
   var _no , _name, _age ;
   var checkNo = function (no)
   {
    if (!no.constructor == "string" || no.length != 4)
     throw new Error("学号必须为4位");
   };
   this.setNo = function (no)
   {
    checkNo(no);
    _no = no;
   };
   this.getNo = function ()
   {
    return _no;
   }
   this.setName = function (name)
   {
    _name = name;
   }

   this.getName = function ()
   {
    return _name;
   }

   this.setAge = function (age)
   {
    _age = age;
   }
   this.
     getAge = function ()
   {
    return _age;
   }

   this.setNo(no);
   this.setName(name);
   this.setAge(age);
  }
  Person.prototype = {
   constructor: Person,
   toString: function ()
   {
    return "no = " + this.getNo() + " , name = " + this.getName() + " , age = " + this.getAge();
   }
  }
  ;
  var p1 = new Person("0001", "小平果", "22");
  console.log(p1.toString());  //no = 0001 , name =小平果 , age = 22
  p1.setNo("0003");
  console.log(p1.toString());  //no = 0003 , name = 小平果 , age = 22
  p1.no = "0004";
  console.log(p1.toString()); //no = 0003 , name = 小平果 , age = 22

 </script>

<script type="text/javascript">

  var Person = (function ()
  {
   //静态方法（共享方法）
   var checkNo = function (no)
   {
    if (!no.constructor == "string" || no.length != 4)
     throw new Error("学号必须为4位");
   };
   //静态变量（共享变量）
   var times = 0;

    //return the constructor.
   return function (no, name, age)
   {
    console.log(times++); // 0 ,1 , 2
    var no , name , age; //私有变量
    this.setNo = function (no) //私有方法
    {
     checkNo(no);
     this._no = no;
    };
    this.getNo = function ()
    {
     return this._no;
    }
    this.setName = function (name)
    {
     this._name = name;
    }

    this.getName = function ()
    {
     return this._name;
    }

    this.setAge = function (age)
    {
     this._age = age;
    }
    this.getAge = function ()
    {
     return this._age;
    }

    this.setNo(no);
    this.setName(name);
    this.setAge(age);
   }
  })();

  Person.prototype = {
   constructor: Person,
   toString: function ()
   {
    return "no = " + this._no + " , name = " + this._name + " , age = " + this._age;
   }
  };

  var p1 = new Person("0001", "小平果", "22");
  var p2 = new Person("0002", "abc", "23");
  var p3 = new Person("0003", "aobama", "24");


  console.log(p1.toString());  //no = 0001 , name = 小平果 , age = 22
  console.log(p2.toString());  //no = 0002 , name = abc , age = 23
  console.log(p3.toString()); //no = 0003 , name = aobama , age = 24

 </script>