hook_menu implementation for AJAX commands

my_module.module.php

<?php
/**
 * Implements hook_menu().
 */
function MY_CUSTOM_MODULE_menu() {
  // Returns AJAX commands if the user has JavaScript turned on.
  $items['my-custom-path/ajax'] = array(
    'title' => 'My custom ajax callback',
    'page callback' => 'MY_CUSTOM_MODULE_ajax_callback',
    'access arguments' => array('access content'),
    'type' => MENU_CALLBACK,
  );
  // Returns a Non-JavaScript alternative.
  $items['my-custom-path/nojs'] = array(
    'title' => 'My custom non-javascript callback',
    'page callback' => 'MY_CUSTOM_MODULE_nojs_callback',
    'access arguments' => array('access content'),
    'type' => MENU_CALLBACK,
  );
  // The page that will run the command.
  $items['my-custom-path/trigger-page'] = array(
    'title' => 'AJAX trigger page',
    'page callback' => 'MY_CUSTOM_MODULE_trigger_page',
    'access arguments' => array('access content'),
    'type' => MENU_CALLBACK,
  );
  return $items;
}