Drupal 8: Custom AJAX Commands

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.
Aapp is a simple and robust decoupled app that works with Drupal 8 and facilitates simple actions like imports and custom batch jobs that developers can expose to their customers.
This handy JavaScript app, developed for arocom.de web agency, allows searching for contact using ajax without reloading the page.