Chapter 12: JavaScript and the Ajax API

In this chapter, we'll switch gears and talk a bit about frontend development, namely, how to work with JavaScript in a Drupal 9 application. This is because there are many things developers can and should be doing in their modules that require frontend technologies. There are a few approaches and techniques specific to Drupal when it comes to adding and using JavaScript files and we will talk about those here. Moreover, we will also prove how powerful Drupal is in allowing us to do quite a bit of JavaScript work without actually writing a single line of JavaScript code.

So, there are a few things we will cover in this chapter.

First, we will talk about the approach of writing JavaScript in Drupal. You already learned in Chapter 4, Theming, how you can create libraries and attach them to render arrays, elements, or pages. Basically, using libraries, we can get our JavaScript files loaded when we need. I recommend you check out the...