请问一下为什么返回的是NaNNN啥的
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Math </title>
<script type="text/javascript">
var arr = [3.3,-0.1,-9.9,8.9];
for(i=0;i<arr.length;i++)
{
document.write(Math.ceil(arr[i]+"<br/>"));
}
</script>
</head>
<body>
</body>
</html>