function person(name,age){
    this.name = name;
    this.age = age;
}
person.prototype.say = function(){
    console.log(this.name+":"+this.age);
}

function superman(name,age){
    person.call(this,name,age);
}
superman.prototype = new person();

var s = new superman('superman',29);

在书上看到这种继承方式，说很完美，可是我并不觉得啊，因为他的superman.prototype = new person();这句，会将父类的实例属性添加到子类的原型上啊，虽然person.call(this,name,age);已经拿到了父类的实例属性，但是感觉这样污染了子类的原型啊，怎么破？

好了，问题解决了，使用寄生组合式继承可以解决这个问题

function object(obj){
 function F(){}
 F.prototype = obj;
 return new F();
}

function inheritProtoType(SuperType,SubType){
     var prototype = object(SuperType.prototype);
     prototype.constructor = SubType;
     SubType.prototype = prototype;
}

function SuperType(){
    this.name = 'yuhualingfeng';
    this.friends = ['David','Bob','Lucy'];
}
SuperType.prototype.saySuperName = function(){
    console.log(this.name);
};

function SubType(){
    SuperType.call(this);
    this.age = 30;
}
inheritProtoType(SuperType,SubType);

SubType.prototype.saySubName = function(){
    console.log(this.name);
};

var subType = new SubType();