Javascript 闭包和继承

Question

我有两个文件:BaseClass.js 和 DerivedClass.js。内容如下

//---------------------BaseClass.js----------------------------

(function () {
    BaseClass= function() { };
    BaseClass.prototype.getTestVar = function() {
    return 'base test variable';
    };
})();


//----------------DerivedClass.js----------------------------

(function () {
    DerivedClass= function() { };
    DerivedClass.inherits(BaseClass);
    DerivedClass.prototype = new BaseClass();
    DerivedClass.prototype = {
        newvar : 'derived func variable ',
        getNewVar : function() { return this.newvar; }
    };
})();

---

在我的 html 文件“test.html”中，我有以下内容

var dc = new DerivedClass();
alert(
    'The value in newvar of derived class ' + dc.getNewVar() + 
    ' base class variable ' + dc.getTestVar()
);

我收到 Javascript 错误，指出 dc.getTestVar() 不是一个函数。非常感谢任何解决此问题的帮助。

Answer 1

此时:

DerivedClass.prototype = new BaseClass();
DerivedClass.prototype = {
    newvar : 'derived func variable ',
    getNewVar : function() { return this.newvar; }
};

您首先将原型(prototype)设置为 BaseClass，然后用新对象覆盖它。试试这个:

DerivedClass.prototype = new BaseClass();
DerivedClass.prototype.newvar = 'derived func variable ';
DerivedClass.prototype.getNewVar = function() { return this.newvar; };