仔细想了想：有三点可以参考
直接上代码：
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
<title>提交表单页</title>
<script type="text/javascript">
function myCheck()
{
for(var i=0;i<document.form1.elements.length-1;i++)
{
if(document.form1.elements[i].value=="")
{
alert("当前表单不能有空项");
document.form1.elements[i].focus();
return false;
}
}
return true;
}
</script>
</head>
<body>
<form name="form1" method="post" action="page2.html" onsubmit="return myCheck()">
用户名:<input type="text" name="username"><br>
性别:<input type="text" name="sex"><br>
出生时间:<input type="text" name="birthday"><br>
<input type="submit" value="提交">
</form>
</body>
</html>
________________________________________________________________________________________________________________________________
2.
<%--
网站: <a href="http://www.crazyit.org">疯狂Java联盟</a>
author yeeku.H.lee kongyeeku@163.com
version 1.0
Copyright (C), 2001-2014, yeeku.H.Lee
This program is protected by copyright laws.
Program Name:
Date:
--%>
<%@ page contentType="text/html;charset=GBK" errorPage="error.jsp"%>
<!DOCTYPE html>
<html>
<head>
<meta name="author" content="Yeeku.H.Lee(CrazyIt.org)" />
<meta http-equiv="Content-Type" content="text/html; charset=GBK" />
<title> 注册用户 </title>
</head>
<body>
<center>
<div style="width:540px;border:1px solid black;background-color:#ddd">
<form id="regForm" method="post" action="reg.do">
<span style="color:red">
${requestScope.tip}
</span>
<hr/>
<table>
<tr>
<td colspan="2" align="center">
请输入用户名和密码完成注册
</td>
</tr>
<tr>
<td>用户名：</td>
<td><input id="name" type="text" name="name" required="true"/></td>
</tr>
<tr>
<td>密 码：</td>
<td><input id="pass" type="password" name="pass" required="true"/></td>
</tr>
<tr>
<td colspan="2" align="center">
<input type="submit" value="提交"/>
<input type="reset" value="重设"/>
</td>
</tr>
</table>
<br/>
<div align="center">
<a href="index.jsp">登录</a>
</div>
</form>
</div>
</center>
<script type="text/javascript">
function check()
{
var name = document.getElementById("name");
var pass = document.getElementById("pass");
var errStr = "";
if (name.value == "" || name.value == null)
{
errStr += "用户名不能为空\n";
}
if (pass.value == "" || pass.value == null)
{
errStr += "密码不能为空\n";
}
if (errStr == "" || errStr == null)
{
return true;
}
alert(errStr);
return false;
}
document.getElementById("regForm").onsubmit = check;
</script>
</body>
</html>
3.权威版：
