使用闭包来模拟私有成员的访问

  var People =
   function(){
      var _name = arguments[0]; //构造函数
      this.getName = function (){
          return _name;
      };
      this.setName = function(name){
          _name = name;
      };
  }
 var p1 = new People();

 var p2 = new People("aaa");
 alert(p1.getName()); //undifined
 alert(p2.getName()); //xxx
 
 p1.setName("zst");
 alert(p1.getName());