function Father(lastname,sex){
                this.lastname=lastname;    //姓        
                this.sex=sex;//性别    
            }
            //父类原型属性
            Father.prototype.xo=‘xxx‘;
            
            //子类
            function Son(firstname){
                this.firstname=firstname;//名                
            }
                    
            Son.prototype=new Father(‘杨‘); //原型继承,son的原型已经指向了father对象的实例
            
            var son =  new Son(‘清‘);
            alert(son.firstname);//清
            alert(son.lastname);//杨  继承的属性
            alert(son.xo);//xxx  继承的原型属性
            alert(son.sex);//undefined//继承时未传值

            //父类
            function Father(lastname,sex){
                this.lastname=lastname;    //姓        
                this.sex=sex;//性别    
            }
            //父类原型属性
            Father.prototype.xo=‘xxx‘;
            
            //子类
            function Son(lastname,firstname){
                Father.call(this,lastname);//将Father构造函数绑定到Son
                this.firstname=firstname;//名                
            }
                
            var son =  new Son(‘杨‘,‘清‘);
            alert(son.firstname);//清
            alert(son.lastname);//杨  继承的属性
            alert(son.xo);//undefined  未能继承到原型属性
            alert(son.sex);//undefined//不需要继承属性

            function Father(lastname,sex){
                this.lastname=lastname;    //姓        
                this.sex=sex;//性别    
            }
            //父类原型属性
            Father.prototype.xo=‘xxx‘;
            
            //子类
            function Son(lastname,firstname){
                Father.call(this,lastname);//借用构造函数继承
                this.firstname=firstname;//名                
            }
            Son.prototype=new Father(); //原型继承,不用传参 只为继承原型属性
            var son =  new Son(‘杨‘,‘清‘);
            alert(son.firstname);//清
            alert(son.lastname);//杨  继承的属性
            alert(son.xo);//xxx  继承到原型属性
            alert(son.sex);//undefined//不需要继承属性