表单提交判断年龄为数值怎么写

 <%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
    <%@ taglib uri="http://java.sun.com/jstl/core_rt" prefix="c"%>
    <%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<base href="<%=basePath%>">
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>用户添加</title>
<script src="http://lib.sinaapp.com/js/jquery/2.0.2/jquery-2.0.2.min.js">
</script>
<script type="text/javascript">
    function check(form){
        if(form.userName.value==""){
            alert("请输入用户名,不可为空!");
            form.userName.focus();
            return false;
        }

        if(form.password.value==""){
            alert("请输入密码,不可为空!");
            form.password.focus();
            return false;
        }
        if(isNaN()){
            alert("请输入整数年龄!")
            form.age.focus();
            return false;
        }

    }

</script>

</head>
<body >
    <h1 align="center">用户添加界面</h1>

    <form action="<%=path %>/user/save.do"  method="post"  id="formTable" name="form1" >
        <table align="center">

            <tr>

                <td><input type="hidden"   readonly="readonly" id="inputid" name="id"  value="${user.id }" /></td>

            </tr>
            <tr>
                <td>用户名:</td>
                <td><input type="text"  id="userName" name="userName"  value="${user.userName }" /></td>
                <td>(*不可为空*)</td>
            </tr>
            <tr>
                <td>密码:</td>
                <td><input type="password"   id="password" name="password"  value="${user.password }"  /></td>
                <td>(*不可为空*)</td>
            </tr>
            <tr>
                <td>年龄:</td>
                <td><input type="text"  id="age"  name="age"  size="2"  value="${user.age }" /></td>
            </tr>
            <tr>

                <td><input type="submit"   id="submit1" value="保存"   onclick="return check(this.form);"/></td>
                <td>
                <a href="user/userlist.do">
                    <button type="button">返回</button>

                </a>

                </td>
            </tr>
        </table>
    </form>
</body>
</html>

^[0-9]*$ 用正则校验


        if(isNaN(form.age.value)){
            alert("请输入整数年龄!")
            form.age.focus();
            return false;
        }