how to get a form's id?

I want to use a form's id in javascript that runs after the DOM is loaded, so what method would get the form's id for an object? In other words, there will be erb thus:

<%= form_for(@obj) do |f| %>...<% end %>

so what erb would give me the id which that form will get?

I know I can just give the form a custom id as a workaround, but I really do not need to change the id, just know what it is. (I also can calculate it myself pretty easily, but I'd rather use the same method that RoR uses, for future-proofing.)

This is all a very small issue, given the multiple easy workarounds. I'm just surprised that I could not find anything in the docs or forums. (RoR 3.2, BTW.)

Hi Scott, it is an interesting question. I was seeing in the source code and I found that[0]. Basically, rails ask to object if it is persisted or not to create the id.
But this is a private method, then you should need to implement this logic in a helper(?) or something.

[0] https://github.com/rails/rails/blob/7a085dac2a2820856cbe6c2ca8c69779ac766a97/actionview/lib/action_view/helpers/form_helper.rb#L440

Re-implementing would completely defeat the purpose of not using my own id, so I'll just use my own. Thanks for the pointer to the implementation.