javascript中setInterval制作跑马灯的效果

<script type="text/javascript">
        function scroll() {
            var title = document.title;            
            var firstCh = title.charAt(0);
            var lafter = title.substring(1, title.length);
            document.title = lafter + firstCh;
         
        }
        setInterval("scroll()",1000);        
    </script>