function extend(child,parent){

     var F=function(){}

     F.prototype=parent.prototype;

     child.prototype=new F();

     child.prototype=child;

     child.uber=parent.prototype; //uber指向父对象的原型。方便子对象调用父对象原型中的重写的方法。

 }

 function Shape(){}

 Shape.prototype.name="Shape";

 Shape.prototype.color="blue";

 function circle(radius){

     this.radius=radius;

 }

 circle.prototype.name="circle";

 circle.prototype.getS=function(){

     return this.radius*this.radius*3.14;

 }

 extend(circle,Shape);

 var cir=new circle(2);

 alert(cir.name);   //"circle"

 alert(cir.color);    //"blue"

 alert(cir.uber.name);    //"Shape"

 alert(cir.getS()) //"12.56"

 var cir=new circle(2);

 var shape1=new Shape();

 cir.prototype.name="this is circle";

 for(var i in shape1){

      if(!shape1.hasOwnProperty(i)){  //遍历非实例属性

          console.log(i+"："+shape1[i]);

      }

 }

 //name:circle

 //color:blue

 //getS:function (){

     return this.radius*this.radius*3.14;

 }

 for(var i in cir){

      if(!cir.hasOwnProperty(i)){

         console.log(i+"："+cir[i]);

      }

 }

 //name:circle

 //color:blue

 //getS:function (){

     return this.radius*this.radius*3.14;

 }.