Take the 2-minute tour ×  I have a simple form like this one:
<form ENCTYPE="multipart/form-data" action="upload.php"
method="POST"> <p>UPLOAD FILE: <input type="file" name="file1">
<br /></p> <input type="hidden" name="email" id="email"
value="">  I have to set the value of the hidden field to an
email like "email@email.com". I can obtain this value from
adding a querystring parameter by external iframe like:  <iframe
name="email@email.com" src="index.html?email=email@email.com">
Ok. But how can I set value="" to value="email@email.com"? I
know have to use javascript, but I dunno how to deal with the
var.  share|improve this question You could also fill it in on
the server side if you want - you could get your index.html to
use some server-side processing, take the email parameter and
insert it into the field when you generate the form. But it's
easy enough to do this with JavaScript too. –  Rup Jul 9 '12 at
10:46 See this question to extract the query string values. Some
of the solutions may be a bit over