setInterval 無限循環；clearInterval停止；
時鐘循環
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<script>
function loaded(){
var mytime =new Date();
var year=mytime.getFullYear();
var month=mytime.getMonth()+1;
var day=mytime.getDate();
var week=mytime.getDay();
var hours=mytime.getHours();
var min=mytime.getMinutes();
var sec=mytime.getSeconds();
var flog="AM";
switch(week){
case 0:
week="星期天";
break;
case 1:
week="星期一";
break;
case 2:
week="星期二";
break;
case 3:
week="星期三";
break;
case 4:
week="星期四";
break;
}
if(hours>12){
floag="PM";
hours=hours-12;
}
if(hours<10){
hours="0"+hours;
}
if(min<10){
min="0"+min;
}
if(sec<10){
sec="0"+sec;
}
document.getElementById("datetime").innerHTML=year+"年"+month+"月"+day+"日"+hours+":"+min+":"+sec+" "+floag+" "+week;
}
setInterval("loaded()",1000)
</script>
</head>
<body >
<div id="datetime"></div>
</body>
</html>