Introduction
﹟ About Stimulus
Stimulus is a JavaScript framework with modest ambitions. Unlike other front-end frameworks, Stimulus is designed to enhance static or server-rendered HTML—the “HTML you already have”—by connecting JavaScript objects to elements on the page using simple annotations.
These JavaScript objects are called controllers, and Stimulus continuously monitors the page waiting for HTML data-controller attributes to appear. For each attribute, Stimulus looks at the attribute’s value to find a corresponding controller class, creates a new instance of that class, and connects it to the element.
You can think of it this way: just like the class attribute is a bridge connecting HTML to CSS, Stimulus’s data-controller attribute is a bridge connecting HTML to JavaScript.
Aside from controllers, the three other major Stimulus concepts are:
- actions, which connect controller methods to DOM events using
data-actionattributes - targets, which locate elements of significance within a controller
- values, which read, write, and observe data attributes on the controller’s element
Stimulus’s use of data attributes helps separate content from behavior in the same way CSS separates content from presentation. Further, Stimulus’s conventions naturally encourage you to group related code by name.
In turn, Stimulus helps you build small, reusable controllers, giving you just enough structure to keep your code from devolving into “JavaScript soup.”
﹟ About This Book
This handbook will guide you through Stimulus’s core concepts by demonstrating how to write several fully functional controllers. Each chapter builds on the one before it; from start to finish, you’ll learn how to:
- print a greeting addressed to the name in a text field
- copy text from a text field to the system clipboard when a button is clicked
- navigate through a slide show with multiple slides
- fetch HTML from the server into an element on the page automatically
- set up Stimulus in your own application
Once you’ve completed the exercises here, you may find the reference documentation helpful for understanding technical details about the Stimulus API.
Let’s get started!