function Polygon(iSides) {
            this.sides = iSides;            if (typeof Polygon._initialized == "undefined") {                Polygon.prototype.getArea = function () {
                    return 0;
                }
                Polygon._initialized = true;
            }
        }        function Triangle(iBase, iHeight) {
            Polygon.call(this, 3);
            this.base = iBase;
            this.height = iHeight;            if (typeof Triangle._initialized == "undefined") {                Triangle.prototype = new Polygon();
                Triangle.prototype.getArea = function () {
                    return 0.5 * this.base * this.height;
                };
                Triangle._initialized = true;
            }
        }//这里的this代表的是什么对象  还有这段代码错在什么地方。 本人JS刚学的菜鸟 求各位大牛 解释清楚点  
 Polygon.call(this, 3);
            this.base = iBase;
            this.height = iHeight;