_form.haml

  function reloadSubCategories (category, submenu) {
    if (category && submenu) {
    $.getScript('/admin/categories/'+ category +'/submenus/'+ submenu +'/subcategories', function(){
      var subcat = $('#post_subcategory_id').val();
      $("#new_subcategory").attr("action", '/admin/categories/' + category + '/submenus/' + submenu + '/subcategories')
      $('#new_post').attr('action', '/admin/categories/' + category + "/submenus/" + submenu + '/subcategories/' + subcat + '/posts')
      });
    } else {
      console.log("miss1")
      $('#post_subcategory_id').empty();
      var subcat = $('#post_subcategory_id').val();
      $('#new_post').attr('action', '/admin/categories/' + category + "/submenus/" + submenu + '/subcategories/' + subcat + '/posts')
    }
  }
  $('#post_category_id').parent().on('change', '#post_category_id', function(e){
    var cat = this.value;
    $('#submenu_category_id').val(cat)
    $('#new_submenu').attr('action', '/admin/categories/' + cat + '/submenus')

    $.getScript('/admin/categories/' + this.value + '/submenus', function(e){
      var submenu = $('#post_submenu_id').val();
      reloadSubCategories(cat, submenu);
    })
  });

  $('#post_submenu_id').parent().on('change', '#post_submenu_id', function(e){
    var cat = $('#post_category_id').val();
    var submenu = $('#post_submenu_id').val();
    $('#subcategory_submenu_id').val(submenu);
    reloadSubCategories(cat, submenu);
  });

  $('#submenu_category_id').parent().on('change', '#submenu_category_id', function(e){
    $('#new_submenu').attr('action', '/admin/categories/' + this.value + '/submenus')
  })
  $('#subcategory_submenu_id').parent().on('change', '#subcategory_submenu_id', function(e){
    var cat = $('#post_category_id').val();
    $('#new_subcategory').attr('action', '/admin/categories/' + cat + '/submenus/'+ this.value + '/subcategories')
  })


  $('#post_subcategory_id').parent().on('change', '#post_subcategory_id', function(e){
    console.log("I caught the change of the subcategory")
    var subcatVal = $(this).val();
    var category = $(this).closest("form").find("#post_category_id").val();
    var submenu = $(this).closest("form").find("#post_submenu_id").val();
    $('#new_post').attr('action', '/admin/categories/' + category + "/submenus/" + submenu + '/subcategories/' + subcatVal + '/posts')
  })

create.js.erb

var foo = $("#submenu_category_id option:selected").val()

$("#post_category_id").val(foo);
$("#post_submenu_id, #subcategory_submenu_id").replaceWith("<%= escape_javascript(render("updated_submenus")) %>");
$("#submenu_title").val("");

var bar  = $("#post_submenu_id").val();

var cat = $("#post_category_id").val();

$("#post_subcategory_id").val("")
$("#subcategory_submenu_id").val(bar)
$("#createsubmenu").modal('hide');

var submenu = $("#post_submenu_id").val();
console.log(foo)

$("#new_subcategory").attr("action", '/admin/categories/' + cat + '/submenus/' + submenu + '/subcategories')
$('#new_post').attr('action', '/admin/categories/' + cat + "/submenus/" + submenu + '/subcategories/' + "null" + '/posts')