JavaScriptでのレプリケーション継承

    <script type="text/javascript">
        $(function () {
            //     
            function Tiger() {
                this.addr = "dongbei";
                this.climb = "       ";
            }

            // Tiger        extend
            Tiger.prototype.extend = function (obj) {
                //  obj                
                for (var i in obj) {
                    //       extend  
                    //           
                    if (this[i] == undefined) {
                        this[i] = obj[i];
                    }
                }
            }
            var kitty = {color: 'yellow', climb: '  '};
            var black = new Tiger();
            //  kitty          black  
            black.extend(kitty);
            console.log(black);
        });

    </script>