为什么结果是是undefined,其它两个变量都正常，请教

function Base() {}

Base.extend = function(obj) {
//顶级构造
var Class = obj['constructor'];
//解析传入的对象实现构造函数
for(var i in obj) {
if(i != "constructor") {
Class.prototype[i] = obj[i];
}
}

Class.extend = function(objChild) {
var ChildClass = objChild['constructor'];

//继承父类的prototype方法
            ChildClass.prototype = this.prototype;

//提供base方法调用父类的构造
ChildClass.prototype.base = function() {
obj['constructor'].apply(this, arguments)
}
            
//解析传入的对象实现构造函数
for(var k in objChild) {
if(k != "constructor") {
ChildClass.prototype[k] = objChild[k];
}
}

//子类的子类也有继承的特性
ChildClass.extend = Class.extend;

return ChildClass;

}
return Class;
}

var Person = Base.extend({
constructor: function(name) {
this.name = name;
},
getName : function() {
return this.name;
}
});

var User = Person.extend({
constructor: function(name, password) {
this.base(name);
this.password = password;
},
getPassword : function() {
return this.password;
}

});

var ArchiveUser = User.extend({
constructor: function(name, password, isAdmin) {
this.base(name, password);
this.isAdmin = isAdmin;
},
getAdmin : function() {
return this.isAdmin;
}
});


var archiveUser = new ArchiveUser("Jack", "123", 1);

alert(archiveUser.getPassword());

constructor function prototype javascript
[解决办法]
21行代码有问题。

obj['constructor'].apply(this, arguments);

这里的obj['constructor']是你顶级构造的那个构造函数，就是你代码里的Person

所以不会执行User的构造函数。

所以也就不会有password属性了
[解决办法]
改了一下，这样就出来了，不知道跟你想要的是一样东西么。

    function Base() {}
         
    Base.extend = function(obj) {
        //顶级构造
        var Class = obj['constructor'];
        //解析传入的对象实现构造函数
        for(var i in obj) {
            if(i != "constructor") {
                Class.prototype[i] = obj[i];
            }
        }
        Class.parent = Base; 
 
        Class.prototype.base = Class;
        Class.extend = function(objChild) {
            var ChildClass = objChild['constructor'];
            ChildClass.parent = this;
            //继承父类的prototype方法
            ChildClass.prototype = this.prototype;
             
            //解析传入的对象实现构造函数
            for(var k in objChild) {
                if(k != "constructor") {
                    ChildClass.prototype[k] = objChild[k];
                }
            }
             
            //子类的子类也有继承的特性
            ChildClass.extend = function(){
                return Class.extend.apply(this,arguments);
            }
             
            return ChildClass;
                 
        }
        return Class;
    }
     
    var Person = Base.extend({
        constructor: function(name) {
            this.name = name;
        },
        getName : function() {
            return this.name;   
        }
    });
     
    var User = Person.extend({
        constructor: function(name, password) {
            User.parent.call(this,name);
            this.password = password;
        },
        getPassword : function() {
            return this.password;   
        }
         
    });
     
    var ArchiveUser = User.extend({ 
 
        constructor: function(name, password, isAdmin) {
            ArchiveUser.parent.call(this,name,password);
            this.isAdmin = isAdmin;
        },
        getAdmin : function() {
            return this.isAdmin;   
        }   
    });
    console.log(Person.parent.toString())     
    console.log(User.parent.toString())     
    console.log(ArchiveUser.parent.toString())
    var archiveUser = new ArchiveUser("Jack", "123", 1);
    console.log(archiveUser);