Dropdown menu with form data?

Hey there,

I'm building a dropdown menu for a form, that looks something like this:

• Entry 1
• Subset
  • Entry 1
  • Entry 2
• Entry 2

The selected option has to be in the params later on.

I'm a React dev and know how to build the dropdown menu itself, but how do I wire JS and Rails in this case?
Do I need an AJAX controller, only for the menu? How do I use it in JS?

Solved it..

I just had honey in my head.

All you have to do is render a hidden field that you update on click and just render all ul's and li's and toggle their display with jQuery.