<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<script type="text/javascript">
function isLeapYear(year){
if((year%4==0)&&(year%100!=0)||(year%400==0)){
return year+"是闰年";
}else{
return year+"不是闰年";
}
}
document.write(isLeapYear(2021));
</script>
</head>
<body>
</body>
</html>