var Gadget = function(price) {

     this.price = price;

 }

 Gadget.isShiny = function(){

     var msg = 'you bet';//公有静态

     if(this instanceof Gadget){//实例调用时

         msg += ', it costs ' + this.price + '!';

     }

     return msg;

 }

 Gadget.prototype.isShiny = function(){

     return Gadget.isShiny.call(this)

 }

 console.log(Gadget.isShiny());//you bet  此为静态调用

 var a = new Gadget(23);

 console.log(a.isShiny());//you bet, it costs 23!   此为实例调用

 var Person;

 (function(){

     var id = 0;//私有

     Person = function(){

         id ++;

         this.id = id;

     }

     Person.prototype.getId = function(){

         console.log(this.id);

     }

     Person.prototype.getLastId = function(){

         console.log(id);

     }

 })();

 var p1 = new Person();

 p1.getLastId();//

 p1.getId();//

 var p2 = new Person();

 p2.getLastId();//

 p2.getId()//

 var p3 = new Person();

 p3.getLastId();//

 p3.getId();//

 p1.getId();//

 p2.getId();//

 p3.getId();//