Adding stylesheets (CSS) and JavaScript (JS) to a Drupal module
https://www.drupal.org/docs/creating-custom-modules/adding-stylesheets-css-and-javascript-js-to-a-drupal-module
Core AJAX Callback Commands
https://www.drupal.org/docs/drupal-apis/ajax-api/core-ajax-callback-commands
Drupal 9: Cascading Ajax Select Forms
https://www.hashbangcode.com/article/drupal-9-cascading-ajax-select-forms
Taming JavaScript in Drupal (Includes FAQs)
Sagar Chauhan, Specbee, Feb 07, 2023
https://www.specbee.com/blogs/taming-javascript-in-drupal
Talks about the Drupal behaviors and contexts.
Drupal 9: Creating Ajax Dialogs
Philip Norton, Hash Bang Code, Oct 30, 2022
https://www.hashbangcode.com/article/drupal-9-creating-ajax-dialogs
JavaScript and Events - The Fundamentals
Andy Blum, Lullabot, Sep 7, 2022
https://www.lullabot.com/articles/javascript-and-events-fundamentals