ASP 在客户端判断表单是否为空的代码

<form action="123.asp" method="post" name="form1">

<input type="text" name="username" size="14" >
<input type="password" name="pwd" size=9 />
<input type="submit" name="Submit" value="登陆" />

</form>

我希望对表单中输入的数据进行判断，如果输入的数据为空，则弹框提示不能为空，并且表单不提交，不为空的时候，就提交表单，代码要怎么写呢

<script>
function nclick()
{
if(document.form1.username.value=="")
{
alert("用户名不能为空！")
return false;
}
if(document.form1.pwd.value=="")
{
alert("密码不能为空！")
return false;
}
return true;
}
</script>

<form action="123.asp" method="post" name="form1" onsubmit="return nclick()">

<input type="text" name="username" size="14" >
<input type="password" name="pwd" size=9 />
<input type="submit" name="Submit" value="登陆" />

</form>

<form action="123.asp" method="post" name="form1" onsubmit="check()">

<input type="text" name="username" size="14" > <input type="password" name="pwd" size=9 /> <input type="submit" name="Submit" value="登陆" />

</form> <script language="vbscript"> sub check()

if form1.username.value="" Then MyVar = MsgBox ("请输入用户名",48,"系统错误") window.event.returnvalue=false

else if form1.pwd.value="" Then MyVar = MsgBox ("请输入密码",48,"系统错误") window.event.returnvalue=false End If

End If End sub</script>

呵呵 给楼上补充一下 调用: onsubmit="return checkform(theform)"

<script language="javascript"> function checkform(theform) { if (theform.username.value==""){ theform.username.focus(); alert ("用户名不能为空，请重新输入!"); return false; }

if (theform.password.value==""){ theform.password.focus(); alert ("密码不能为空，请重新输入!"); return false; } } </script>