[セットトップ]JavaScript類継承実現の一つ

var Person = function() {
    this.name = "people";
    this.hello = function() {
      console.log("hello user:" + this.name);
    }
}

var User = function() {
    this.name = "user";
    this.hello = function() {
      User.prototype.hello.call(this, arguments);
      console.log("hello user:" + this.name);
    }
}

User.prototype = new Person();
new User().hello();

(function() {
    Function.prototype.extend = function(baseClass) {

        // this is a function object.
        var oldPrototype = this.prototype, newPrototype = {}, _super = new baseClass();

        //inherits all properties and methods.
        for ( var name in _super) {
            newPrototype[name] = _super[name];
        }

        for ( var name in oldPrototype) {
            // only override properties in this new Class.
            if (oldPrototype.hasOwnProperty(name)) {
                // only function need _super.
                if (typeof oldPrototype[name] == "function" && typeof _super[name] == "function") {
                    newPrototype[name] =  (function(name, fn) {
                            return function() {
                                var tmp = this._super;
                                
                                // set super method
                                this._super = _super[name];

                                var ret = fn.apply(this, arguments);
            
                                this._super = tmp;
            
                                return ret;
                            };
                        })(name, oldPrototype[name]);
                } else {
                    newPrototype[name] = oldPrototype[name];
                }
            }
        }

        this.prototype = newPrototype;
        
        return this;
    };
})();

var A = function() {
    this.hello = function() {
        console.log("hello, I'm A");
    }
};

var B = function() {};

B.prototype = {
    hello : function() {
        this._super();

        console.log("hello, I'm B");
    }
};

B.extend(A);

var C = function() {};

C.prototype = {
    hello : function() {
        this._super();

        console.log("hello, I'm C");
    }
};

C.extend(B);

var b = new B();
var c = new C();

//b.hello();
c.hello();

hello, I'm A
hello, I'm B
hello, I'm C