问题描述

javascript高级程序设计P172的代码

我不太理解为什么constructor需要重新指向subType。我试过删掉那行（prototype.constructor = subType;）效果都一样。

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

        function inheritPrototype(subType, superType){
            var prototype = object(superType.prototype);   //create object
            prototype.constructor = subType;               //augment object
            subType.prototype = prototype;                 //assign object
        }

        function SuperType(name){
            this.name = name;
            this.colors = ["red", "blue", "green"];
        }

        SuperType.prototype.sayName = function(){
            alert(this.name);
        };

        function SubType(name, age){
            SuperType.call(this, name);

            this.age = age;
        }

        inheritPrototype(SubType, SuperType);

        SubType.prototype.sayAge = function(){
            alert(this.age);
        };

        var instance1 = new SubType("Nicholas", 29);
        instance1.colors.push("black");
        alert(instance1.colors);  //"red,blue,green,black"
        instance1.sayName();      //"Nicholas";
        instance1.sayAge();       //29

        var instance2 = new SubType("Greg", 27);
        alert(instance2.colors);  //"red,blue,green"
        instance2.sayName();      //"Greg";
        instance2.sayAge();       //27