<meta http-equiv="refresh" content="20" >
<body onload="reciprocal()">
<span id="showtime"></span> 秒後刷新頁面…
var s = 20;
function reciprocal(){
document.getElementById("showtime").innerHTML=s;
setTimeout(reciprocal,1000);
s -= 1;
}
<meta http-equiv="refresh" content="20" >
<body onload="reciprocal()">
<span id="showtime"></span> 秒後刷新頁面…
var s = 20;
function reciprocal(){
document.getElementById("showtime").innerHTML=s;
setTimeout(reciprocal,1000);
s -= 1;
}