<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>广告框自动关闭</title>
<style>
.ad {
width: 400px;
height: 200px;
position: fixed;
top: 100px;
left: 400px;
background-color: blue;
border: 2px solid black;
}
</style>
<script>
window.onload = function() {
var ad = document.getElementById("ad");
var num = document.getElementById("num");
var count = 5;
var timer = setInterval(function() {
count--;
if(count == 0) {
ad.style.display = "none";
clearInterval(timer);
}
num.innerHTML = count;
}, 1000)
}
</script>
</head>
<body>
<div id="ad" class="ad">我是广告框<span id="num">5</span>s后消失</div>
</body>
</html>
