base_conttoller.rb

module Customer
  class BaseController < ApplicationController
    # ...
    
    before_filter :enable_live_notifications, only: [:waiter_home, :cook_home]
    
    # ...
    
    private
    
    def enable_live_notifications
      @live_notifications_channel = @venue.live_notifications_channel
    end
  end
end

layout.html.erb

<%# ... %>
<span data-live-notifications-channel="<%= @live_notifications_channel %>"></span>

live_notifications.js.coffee

$ ->
  config = $('[data-live-notifications-channel'])
  
  if config
    channel = config.attr 'data-live-notifications-channel'
    
    if channel
    # ...