I want to set hidden input value(username) based on client other input(email) in a form, then submit to server. (to make sure username equal to email)

However, the assignment to the hidden input is processed AFTER the form submitted. So 'username' is already None on server side.

<form id=altForm action= method=post>



<input type=hidden name=username id=id_username maxlength=40 >



<input type=email name=email id=id_email maxlength=40>



<input class=btn btn-primary pull-right type=submit value=Register />

</form>

<script>



    $(#altForm).submit(function(e){

        e.preventDefault();

        var username = $(#id_email).val();

        $(#id_username).val(username);



    });



</script>