Use Ajax in ruby on rails

I want send selected drop down menu value to controller by ajax

panel_controller.rb

class PanelController < ApplicationController

      def insert
         @city_ids = params[:city]
      end
end

panel.js.erb

$(document).ready(function() {
    $('#f_city_id').change(function() {
        var city_js_id = this.value
        $.ajax({
            url: '/panel/insert',
            type: 'GET',
            data: {"city": city_js_id},
            success: function (data,status)
            {
                alert(this.url);
            }
        });
        return false;
    });
});

routes.rb

get '/panel/insert' => 'panel#insert'

views/panel/insert.html.erb

<%= @city_ids %>

but @city_ids dont respond value after chenge drop down menu