I am in the process of converting my asp pages from vbScript to 
JavaScript.  However, I am strugeling to convert a form processing 
action.  for example

in vbScript it reads
<% If (Request.Form.Item("usernumber") = "") then %>

<form action=[samepage.asp]>
<input type=text name="usernumber">
<input type = submit etc>

<%
else
%>
Response.Write (Request.Form.Item ("usernumber") )
end if
%>

can anybody tell me how to wright the first line in JavaScript
Thanks