JavaScript实现倒计时自动关闭广告

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>Title</title>
 <style>
 .djs{
 width: 30px;
 height: 30px;
 position: absolute;
 left: 700px;
 color: white;
 background-color: darkred;
 }
 .end{
 display: none;
 }
 </style>
</head>
<body>
<div class="djs"></div>
<img class="ad" src="../images/1.png" alt="">
<div class="end">广告已结束</div>
<script>
 //5秒关闭广告
 var ad=document.querySelector('.ad')
 var div=document.querySelector('.djs')
 var end=document.querySelector('.end')
 var t=5
 fun()
 setInterval(fun,1000)
 function fun() {
 div.innerHTML=t
 if (t==0){
 ad.style.display='none'
 div.style.display='none'
 end.style.display='block'
 }
 t--
 }
</script>
</body>
</html>