When changing the ajax responses with hook_ajax_render_alter(), you may sometimes want to add a custom ajax command. Drupal 8 actually supports a plugin-like functionality for it. This functionality needs to be served by a custom module and consists of 2 files - a src/Ajax class and a javascript file implementing the command.
1. The Ajax class file.
src/Ajax/MyCommand.php
<?php
namespace Drupal\mymodule\Ajax;
use Drupal\Core\Ajax\CommandInterface;
/**
* Set mymodule key.
*
* This command is implemented in Drupal.AjaxCommands.prototype.myCommand.
*/
class MyCommand implements CommandInterface {
/**
* Assigned data.
*
* @var mixed
*/
protected $data;
/**
* Constructs a \Drupal\mymodule\Ajax\MyCommand object.
*
* @param string $key
* Key name.
* @param mixed $value
* Assigned value.
*/
public function __construct($data) {
$this->data = $data;
}
/**
* {@inheritdoc}
*/
public function render() {
return [
'command' => 'myCommand',
'data' => $this->data,
];
}
}
?>2. The Javascript Implementation.
/**
* @file
* JavaScript behaviors for Ajax.
*/
(function ($, Drupal) {
/**
* Sample command.
*
* @see Drupal.AjaxCommands
*/
Drupal.AjaxCommands.prototype.myCommand = function (ajax, response) {
console.log(response.data);
};
})(jQuery, Drupal);