Enctype Error

[Stephen Wei]

Hello all:
I am uploading a file to my servlet. Before doing so, on the client side I use Javascript to check if the file is csv or not. The checking is ok, but then my servlet says Enctype error.
Notice that if I remove the Javacript checking, the file is uploading fine. So what is wrong with my approach? how to fix it?
Following is my code, thanks.
<script language = "javascript">
function fileFormSubmit()
{
var error1 = "please select csv file";
var error2 = "please select GIF file";
window.event.returnValue = false;
var string = uploadForm.fileName.value.substr((uploadForm.fileName.value.lastIndexOf(".")+1));

if ((string != "csv")&&(string != "CSV"))
{
alert(error1);
uploadForm.fileName.onfocus;
}
else{
if(confirm("submit?")){
window.event.returnValue = true;
}
}

return(0);
}
</script>

<form ID="uploadForm" action="../servlet/Upload" METHOD=POST ENCTYPE="multipart/form-data" onsubmit = "fileFormSubmit()">
<p align="center"> <INPUT TYPE=FILE NAME=file1> </p>
<p align="center"> <INPUT TYPE=SUBMIT> </p>
</form>