<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<script type="text/javascript">
function formCheck(){//表单验证
var userForm=document.forms.userForm
if(userForm.username.value==null||userForm.username.value.length<=0){
alert("用户名不能为空")
return false
}else if(userForm.username.value.length<6||userForm.username.value.length>20){
alert("用户名必须为6-20位")
return false
}else if(userForm.password.value==null||userForm.password.value.length<=0){
alert("密码不能为空")
return false
}else if(userForm.password.value.length<6||userForm.password.value.length>20){
alert("密码必须为6-20位")
return false
}else{
userForm.submit()
}
}
</script>
</head>
<body>
<form action="" name="userForm">
userName:<input type="text" name="username"><br>
password:<input type="password" name="password"><br>
<input type="button" value="提交" onclick=" formCheck()">
</form>
</body>
</html>
用js把文本框清空只需要在input定义中加入clientidmode="Static"，即将<inputtype="text" id="region" runat="server"readonly="readonly" style="border:0pxfont-weight:bold"/>改为<input type="text"id="region" runat="server" clientidmode="Static" readonly="readonly"style="border:0pxfont-weight:bold"/>，这样脚本生成的id为region。
再利用JS清空值，document.getElementById("region").value=""
