即空性验证
<form name="login" id="login" method="POST" action="URL" onsubmit="return checkform();">
用户名:<input type="text" id="username" name="username" />
密 码:<input type="password" id="password" name="password" />
<input type="submit" value="登陆"/>
<form/>
<script type="text/javascript">
function checkform()
{
if(document.getElementById('username').value=='')
{
alert('用户名不能为空!');
return false;
}
if(document.getElementById('password').value=='')
{
alert('密码不能为空!');
return false;
}
}
</script>
用户名:<input type="text" id="username" name="username" />
密 码:<input type="password" id="password" name="password" />
<input type="submit" value="登陆"/>
<form/>
<script type="text/javascript">
function checkform()
{
if(document.getElementById('username').value=='')
{
alert('用户名不能为空!');
return false;
}
if(document.getElementById('password').value=='')
{
alert('密码不能为空!');
return false;
}
}
</script>
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