如题。输入非法数据为什么不报错呢？
<html>
<head>
<title>register info</title>
<meta http-equiv="Content-Type" content="text/html;charset=gb2312">
</head>
<script>
function check(){
username=document.form1.value;
pwd1=document.form1.pwd1.value;
pwd2=document.form1.pwd2.value;
year=document.form1.year.value;
month=document.form1.month.value;
day=document.form1.day.value;
email=document.form1.email.value;
interest=document.form1.interest.value;
if(username.length<6||username.length>15){
alert("usename must be 5-15char");
return false;
}
if(pwd1!=pwd2){
alert("password is not correct!");
return false;
}
if(year.lenth!=4||month>13||month<1||day>32||day<1{
alert("birthday is incorrect!")
return false;
}
if(email=""||(email.indexof('@'==-1)||(email.indexof('.')==-1)){
alert("email format is incorrect!")
return false;
}
return true;
}
</script>
<body bgcolor="#FFFFFF" text="#000000">
<p align="center">input register info</p>
<form name="form1" method="post" action="register.jsp" OnSubmit="return check();">
<table width="36%" border="1" cellspacing="1" cellpadding="1"
align="center" height="160">
<tr>
<td width="45%">username(6-15)bit</td>
<td width="55%">
<input type="text" name="username" size="15">
</td>
</tr>
<tr>
<td width="45%">password(6-10)bit</td>
<td width="55%">
<input type="password" name ="pwd1" size="10">
</td>
</tr>
<tr>
<td width="45%">password confirm</td>
<td width="55%">
<input type="password" name ="pwd2" size="10">
</td>
</tr>
<tr>
<td width="45%">birth day</td>
<td width="55%">
<input type="text" name ="year" size="4">
year
<input type="text" name ="month" size="2">
month
<input type="text" name ="day" size="2">
day</td>
</tr>
<tr>
<td width="45%">sex</td>