js记录用户停留时间的代码

js记录用户停留的时间，代码：

<script language="javascript">
var second = 0;  
var minute = 0;  
var hour = 0;  
var time;  
window.setTimeout("staytime();", 1000);  
  
function staytime() {  
    second++;  
    if (second == 60) { second = 0; minute += 1; }  
    if (minute == 60) { minute = 0; hour += 1; }  
    window.onbeforeunload = function () {
       alert(time);  
    }  
    time = hour + "小时" + minute + "分" + second + "秒";
    window.setTimeout("staytime();", 1000);
}
</script>