setTimeout
setTimeout(function(){},1000)//隔一秒后执行函数；类似闹钟；
广告弹出效果：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style>
div{
width:400px;
height:400px;background:#fbb;
position:fixed;
right:0px;
bottom:0px;
display:none;
}
</style>
</head>
<body>
<div></div>
<script>
var oDiv=document.getElementsByTagName('div')[0];
setTimeout(function(){
oDiv.style.display='block';
setTimeout(function(){
oDiv.style.display='none';
},5000)
},2000);
</script>
</body>
</html>
