1.  获取页面元素, 简化document.getElementById 只用, 可返回对象数组
    function $()
        {
            var elements = new Array();
            for (var i = 0; i < arguments.length; i++)
            {
                var element = arguments[i];
                if (typeof element == 'string')
                  element = document.getElementById(element);
                if (arguments.length == 1)
                  return element;
                elements.push(element);
            }
            return elements;
        }