用户在网页的逗留时间

  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);        }