Sometimes your JavaScript needs to insert new strings into the user interface. In order to ensure that those user-facing strings can be translated into other languages, just like the rest of Drupal's user interface, you should make sure and use the Drupal.t function anytime you output a string of text.

If you want to create a link to an internal page in a Twig template--and there's not already a variable in the template that contains the URL you want to link to--you'll need to determine the route of the thing you want to link to and then use the Twig url() or path() functions to generate appropriate URLs. In most cases when you want to create a link to an entity that is being output by the current template there's an existing helper variable to use. For example, in a node.html.twig template file there's a url variable that points to the current node. For other scenarios, like hard-coding a link to the /about page, you'll need to do a little more work.

In this tutorial, we'll:

• Get the absolute URL value
• Get the relative path value
• Generate HTML for a link
• Get the URI to a file, like an image in the Media library
• Get the active theme path

By the end of this tutorial you should be able to create links to any internal page via Twig.

Twig is the default template engine for Drupal. If you want to make changes to the markup that Drupal outputs you're going to need to know at least some Twig. In this tutorial, we will outline the role that Twig now plays in Drupal, how Twig impacts the theming experience, and where to find additional resources for learning Twig.

At the end of this lesson, you'll be able to:

• Describe the role that Twig plays in creating Drupal themes
• Explain how Twig impacts the theming experience in Drupal
• Locate additional resources for learning Twig

In Twig, you can modify variables using functions or filters. Twig has a bunch of built-in functions and filters. Drupal extends Twig to provide a few handy Drupal-specific functions and filters.

In this tutorial, we'll look at:

• What are functions and filters?
• How to use functions and filters in Twig
• Detailed information about the Drupal-specific functions and filters, and their use case

To read a Twig template file, you'll need to recognize Twig's syntax delimiters. Twig has three syntax delimiters: one for printing out variables, another for performing actions or logic, and lastly, one for comments, also used for docblocks.

In this tutorial we'll:

• Explore each of Twig's 3 syntax delimiters.
• Show examples of each from Drupal's core template files.

By the end of this tutorial you should be able to recognize each of Twig's syntax delimiters and understand what the engine will do when it encounters them.

More often than not, templates in a theme share common elements: the header, footer, sidebar, or more. In Drupal, themes created with a Twig template can be decorated by another one. This template inheritance allows you to build a base "layout" template that contains all the common elements of your layout defined as blocks. A child template can extend the base layout and override any of its defined blocks. This helps prevent code duplication, and keeps your theme more organized.

This tutorial is for theme developers who want to reduce code duplication in their themes, or anyone seeking to better understand how Twig template inheritance works. We'll cover:

• What the Twig block and extends tags do
• An example use-case for template inheritance
• How to extend a Twig template from another theme or module
• How to include other Twig templates

Do you cringe at the sight of untidy whitespace or (gasp) no whitespace at all when you View Source? Learn how to tame whitespace in Twig template files in this tutorial. By the end of this lesson, you will be able to recognize how Twig controls whitespace and how you can do the same in your Drupal template files.

Make your theme a subtheme of a base theme, allowing it to inherit all the base theme's templates and other properties. When creating Drupal themes it is common to use the Classy theme provided with Drupal core as a base theme to jumpstart your development.

In this tutorial we'll learn how to:

• Use the base theme key in our theme's THEMENAME.info.yml file
• Make our Ice Cream theme inherit from the Classy theme, or any other theme

By the end of this tutorial you should be able to tell Drupal that your theme is a child of another theme and should inherit all of the parent theme's features.

The Drupal core Media Library module provides an enhanced user interface for locating Media entities and attaching them to an article. It's a drop-in replacement for the default entity reference widget which uses a not very intuitive autocomplete field. Using the Drupal core Media Library module requires minimal configuration.

If you want to provide content creators with a gallery-like library of Media entities that they can browse through in order to find the ones they want to add to their content, the Media Library is the easiest way to do it. It can be configured to work with both Media fields and the CKEditor powered WYSIWYG editor commonly used for editing the body field of Drupal nodes. There's really no reason not to use it.

In addition to providing a better UI for locating existing Media entities, the Media Library provides a way to create new Media entities right from the content creation form. This prevents an otherwise confusing requirement where Media entities need to be created, via a different set of forms, before they can be used.

In this tutorial we'll:

• Install and configure the Media Library module to work with Media fields
• Use the user interface provided by the Media Library to improve the experience of finding and selecting Media entities to associate with a piece of content

By the end of this tutorial you'll know how to replace the default entity reference widget used for selecting Media entities with the much improved Media Library UI.

Media entities, like any content entity, work great with all the different features Drupal provides for changing the way things are displayed: view modes, Layout Builder, theme templates, and more. We're big fans of using view modes to create a component-like design system where entity types have view modes representing the different context in which they're displayed. Then we theme the view modes. This works great for displaying Media entities associated with a page and for changing the way that Media assets are displayed within the Media Library browser.

In this tutorial we'll:

• Create Hero and Sidebar view modes for Media entities
• Configure the Image Media type to use the new view modes and style each one differently
• Use the new view modes to render Image Media assets within a Layout
• Update the Media library view mode that's used by the Media Library browser to display additional information alongside the thumbnails used when selecting Media to attach to a page

By the end of this tutorial you should be able to change the way that Media assets are displayed by using view modes and display formatters in a Drupal site.

The Render API consists of two parts: structured arrays that provide data and hints about how that data should be rendered, and a rendering pipeline that can be used to render these arrays into various output formats. Understanding at least the basics of how the Render API works, the difference between elements and properties, and the concept of callback functions is an integral part of learning Drupal.

In this tutorial we'll:

• Look at the fundamentals of the Drupal Render API
• Point to additional material to provide more detail about the inner workings of the Render API and how content is output in Drupal

The core structure of Drupal's Render API is the render array, which is a hierarchical associative array containing data to be rendered and properties describing how the data should be rendered. As a module developer you'll use render arrays to describe the content your module controls in order to output it on a page as HTML, or as part of a response in another format like JSON. As a theme developer, you'll manipulate render arrays in order to affect the way content is output on the page.

In this tutorial we'll learn:

• What render arrays are and why they exist
• The basic format of a render array
• What "properties" and "elements" signify in the context of a render array
• Where to find more information about how to create a render array to describe your own content

By the end of this tutorial you should be able to understand when you need to use a render array, recognize one when you see it, and know where to get more detailed information about render array formatting specifics.

One of the central components of Drupal's Render API is render elements. You can think of them as prepackaged render arrays or shortcuts you can use to describe common things, like tables, links, and form elements, in a consistent way. In this tutorial we'll take a more in-depth look at the use of the #type property in render arrays in order to answer questions like:

• What are render elements, and what is their use case?
• Where can I find more information about available element types?

By the end of this tutorial you should be able to identify individual render element types within a larger render array, find the relevant documentation for specific types of render elements, and explain the use case for render elements.

In this tutorial we'll look at how you can use the #theme property of a render array to define custom HTML. With this information, module developers can use render arrays to define content, and theme developers can understand how elements in a render array are converted to HTML and which templates they can override to change the output for a specific element.

Learn how to:

• Use hook_theme() to define a new theme hook and define default values for variables
• Create a corresponding Twig template file that outputs the variables and any custom HTML markup
• Use a preprocess function to add additional variables for the Twig template file you created
• Use the new theme hook in conjunction with a #theme property in a render array to link your Twig template file to actual content

By the end of this tutorial you should know how to define new templates to output content as HTML. You should also have a better understanding of how Twig template files are linked to elements in a render array.

React is a JavaScript library that makes it easy to create interactive user interfaces. Drupal is a content management system with a powerful web services API. React and Drupal can work together in a couple of different ways. This series of tutorials explores some of those options, and the related concepts and terminology.

Our goal is to provide you with some baseline information you can use to get started integrating React and Drupal together. After you've completed these tutorials you should be able to better envision how to use these two technologies to solve some of your own issues. We hope you'll come away from this with enough knowledge to start exploring further on your own. We link to external resources liberally, and encourage you to explore beyond the examples we provide, read the linked resource, and dig in. There's no substitute for exploration and experimenting with real code when it comes to learning these things.

In this series we'll:

• Introduce the technical side of React, terminology, and information about where to find more resources
• Learn about using Drupal, and the JSON:API module, to turn Drupal into a powerful web services API provider
• Learn about the use cases for adding React to a Drupal site
• Walk through increasingly complex code examples that start with a "Hello World!" application, and end with a fully decoupled application that can list, create, update, and delete content in Drupal
• Learn about how to authenticate a Drupal user via an API using React
• Contrast, through example code and use cases, the differences between integrating React into an existing Drupal theme or module and creating a stand-alone React application
• And more!

Before we start writing any React code, let's go over some basic concepts and terminology. Throughout this series we'll assume you're familiar with these things. They'll come up again and again as you work on projects that involve React, so it's worth taking the time to learn them.

In this tutorial we'll cover the following at a high level, and provide links to resources:

• Why choose React?
• What are React components?
• What are hooks, state, and JSX?
• The role of build tools when developing React applications

By the end of this tutorial you should have a firm grasp of the fundamental concepts and terminology necessary to start creating React applications.

React and Drupal can be used together in two different ways: fully decoupled, also known as headless; or progressively decoupled.

In this tutorial we'll talk about the differences between these two approaches, including:

• Defining what each method refers to
• Considerations regarding hosting, performance, and access

Then we'll link to lots of additional reading materials so you can gain a deeper understanding of the subject.

By the end of this tutorial you should be able to define what decoupled and progressively decoupled mean, and how they differ from one another.

Writing a React application requires including the React JavaScript library in the page, writing some React-specific JavaScript, and then binding it to a specific DOM element on the page. You may also want to include existing packages from the npm ecosystem, and use modern JavaScript (ES6+) features, which necessitates setting up a build toolchain for your JavaScript using a tool like Webpack or Parcel.

There are a lot of different ways you could go about setting this all up. Do you add React via a theme or a module? Do you need a build tool? Should you use Webpack, or Babel, or Parcel, or something else? While we can't possibly cover all the different approaches, we can help you figure out what is required, and you can adapt our suggestions to meet your needs.

In this tutorial we'll:

• Create a new custom theme with the required build tools to develop React applications
• Add a DOM element for our React application to bind to
• Create a "Hello, World" React component to verify everything is working

By the end of this tutorial you'll know how to configure everything necessary to start writing React within a Drupal theme.

Components are the fundamental building blocks of any React application. React uses components to represent different elements in the UI. To show this, we'll build a React widget that can query the Drupal.org REST API to retrieve usage statistics for a project and then display them. We'll create buttons that allow us to toggle between two different projects. In doing so we'll learn about creating components and using props and state in React.

In this tutorial we'll:

• Define two new React components
• Learn about using props to pass data to a component
• Learn about using state, and the useState() hook, to create interactivity

By the end of this tutorial you should have a basic understanding of how to write a React component that uses props and state to display data from a third party API.

React excels at displaying lists of data. But that data needs to come from somewhere. In most cases this happens by making a network request to retrieve data from one or more APIs, processing the response, and then displaying the data. In the context of working with a Drupal site there are two possible options: Drupal core's JSON API module, or the drupalSettings JavaScript API.

In this tutorial we'll focus on the high-level overview and:

• Explain the difference between content and configuration data
• Introduce the JavaScript Fetch API, and where to find information about using it
• Get an overview of the ES6 array functions we'll use to parse the complex data structures returned from an API

In the remaining tutorials in this series we'll provide examples of real world use cases.

By the end of this tutorial you should have a firm understanding of how to get started making API requests using React.