Rails 5: jQuery autocomplete json not rendering

Question

I'm trying to implement a JQuery-ui autocomplete on a search form_tag. I have followed this in order to implement it.

This is what I have done thus far but without the desired results:

• Installed the Jquery-ui manually and thus 0 errors show in the browser source inspector.
• I have added the jQuery code for autocompletion.
• I have generated the search_suggestion resource.

And added the following to the search_suggestion_controller.rb in order to test if the json is rendered:

class SearchSuggestionsController < ApplicationController
  def index
    render json: %w[foo bar]
  end
end

But absolutely nothing renders/shows as it is supposed to do!

Does anyone have any idea why this is happening?

Here is my other code:

<%= form_tag items_path, method: :get do %>
  <%= text_field_tag :search, params[:search], autofocus: true, placeholder: 'Enter keyword to search', class: "search-query search_size" %>
  <%= submit_tag 'Search', style: "display: none;" %>
<% end %>

items_controller.rb

def search
  if params[:search]
    @items = Item.search(params[:search]).order("created_at DESC")
    respond_to do |format|
      format.html
      format.json { render json: @items.map(&:title) }
    end
  else
    @items = []
  end
end

item.rb

def self.search(term)
  return where("0=1") if term !~ /\w{4}/
  where("lower(title) LIKE lower(:term)", term: "%#{term}%")
end

items.coffee

jQuery ->
$('#search').autocomplete
 source: "/search_suggestions"