下面的代码哪里出错了，比如不输入用户名或者确认密码不对，都不提示出错信息的
<%@ page language="java" import="java.sql.*" pageEncoding="gb2312"%>
<html>
<script language="javascript">
function chk(){
if(form.username.value.length <1 || form.username.value.length>15){
alert("请输入正确的用户名！");
form.username.focus();
return ;
}
if(form.userpassword.value.length <1 || form.userpassword.value.length>15){
alert("请输入正确的密码！");
form.userpassword.focus();
return ;
}
if((form.userpassword.value!=" ")||(form.reuserpassword.value!=" "){
if(form.userpassword.value!=form.reuserpassword.value){
alert("密码与确认密码不同!");
form.reuserpassword.focus();
return ;
}
}
else{
alert("密码不能为空！");
form.userpassword.focus();
return ;
}
if(form.email.value.length!=0){
for(int i=0;i <form.email.value.length;i++)
if(form.email.value.charAt(i)=="@")
break;
if(i==form.email.value.length){
alter("非法email地址！");
form.email.focus();
return ;
}
}
}
</script>
<body> <br> <br> <br>
<p align="center">
<
