js实现跑马灯效果

<script type="text/javascript">
var str = "欢迎光临";
var strLen = 0;
//设置跑马灯函数
function showTest(){
if(strLen == str.length){
strLen = 0;
}else{
strLen++;
var test = str.substring(0,strLen);
window.status = test;
window.setTimeout("showTest()",1000);
}
}
</script>