<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
</body>
<script type="text/javascript">
var x="abc";
//isNaN()函数判断是否是NaN
if (isNaN(parseInt(x))) {
alert("非数字");
} else{
alert("数字");
}
</script>
</html>
原文：http://www.cnblogs.com/niuniudashijie/p/5988030.html