Front-End , The Drupal way

The Libraries API: Moving away from hard-coding <script> and <link> tags in the header. Understanding how to define assets in *.libraries.yml and attach them conditionally to specific components, ensuring you only load CSS/JS where it is actually used.

Mastering Drupal.behaviors: Why $(document).ready() is often the wrong approach in Drupal. Learning the specific JS pattern that ensures your scripts re-execute correctly after AJAX calls (like Views filtering or pagination) without duplicating events.

Template Suggestions & Debugging: The art of finding the right file to edit. Enabling Twig Debugging to expose HTML comments that tell you exactly which template is rendering a component and providing a list of file names you can create to override it.

The Preprocess Layer: Understanding the power of the .theme file. Learning how to intercept data in PHP (preprocess functions) to clean up variables or add classes before the data ever reaches the Twig template, keeping your HTML clean and logic-free.