Way to get the form name/id from a form_for (default) builder?

Hi all,

I'd like to be able to refer to a form being created by form_for from
javascript. To do this, I'd like to know what will be the id and/or
name that's going to be set on the form. I understand I can override
the id or name, but i'd prefer not to.

For instance, I'm looking for something to fill in

<% form_for :role, ... %>
  <button type="button" onClick="doSomething(document.getElementById('<
%= form.someMethodToGiveMeInputNameFor(:rights) %>')">Press Me</

   <%= form.select(:rights, ... %>
<% end %>

Thanks in advance!