Elm brings the safety and stability of functional programing to front-end development, making it one of the most popular new languages. Elm's functional nature and static typing means that run-time errors are nearly impossible, and it compiles to JavaScript for easy web deployment. This book helps you take advantage of this new language in your web site development. Learn how the Elm Architecture will help you create fast applications. Discover how to integrate Elm with JavaScript so you can update legacy applications. See how Elm tooling makes deployment quicker and easier.

Functional programming offers safer applications with decreased runtime errors, but functional solutions that are type safe and easy to use have been hard to find, until the Elm language. Elm has the benefits of functional languages while compiling to JavaScript. This book provides a complete tutorial for the Elm language, starting with a simple static application that introduces Elm syntax, modules, and the virtual DOM, to exploring how to create a UI using functions. See how Elm handles the issues of state in functional languages. You'll continue to build up larger applications involving HTTP requests for communication. Integrate your Elm applications with JavaScript so you can update legacy applications or take advantage of JavaScript resources.

Elm also provides built-in tooling to alleviate the tooling creep that's so common in JavaScript. This book covers Elm's deployment and testing tools that ease development confusion. Dive into advanced concepts including creating single-page applications, and creating performance improvements. Elm expert Jeremy Fairbank brings his years of web development experience to teaching how to use Elm for front-end development.

Your web UIs will be faster, safer, and easier to develop with Elm and this tutorial.

Contents 

1. Get Started with Elm

2. Creat e Stateful Elm Applications

3. Refactor and Enhance Elm Applications

4. Communicate with Servers

5. Go Real-Time with WebSockets

6. Build Larger Applications

7. Develop, Debug, and Deploy with Powerful Tooling

8. Integrate with JavaScript

9. Test Elm Applications

10. Build Single-Page Applications

11. Write Fast Applications

A1. Install Elm

A2. Run the Local Server

A3. Elm Package Versions

What You Need:

You will need the latest version of Elm, 0.19, along with a browser to run the examples in this book.

Why Elm?

More and more front-end developers are choosing Elm to build applications for benefits such as:

• No runtime exceptions in practice: Elm’s compiler catches problems early to prevent exceptions at runtime for your users.

• No null or undefined errors: Elm offers more versatile types for representing null. The compiler also ensures you handle all possible nulls in your application.

• No JavaScript fatigue: You don’t have to choose and wire up different frameworks and libraries to build an application. Elm has a built-in framework for creating applications, the Elm Architecture.

• Predictable code: All Elm code is free from side effects, so you can trust your functions to always produce the same result based on their arguments.

• Immutable data types: You don’t have to worry about your code or thirdparty code changing data unexpectedly and causing bugs. Your data will be consistent and safe.

• Strong static types: Elm’s compiler uses static types to ensure you call functions with the right types of arguments. You won’t run into subtle type-coercion bugs.

• Custom types: Elm’s custom types let you create entirely new types for clearly modeling your business domain. Powerful pattern matching prevents undefined situations by ensuring you handle your custom types consistently.

• Advanced tools: Elm’s Debug module makes it easy to inspect data to catch bugs and add placeholders to your code until you’re ready to implement it. Third-party tools such as create elm-app let you quickly bootstrap Elm applications and offer powerful development servers for immediate development feedback.

About the Author

**Jeremy Fairbank** is a web developer with a master's degree in computer science. He has many years of experience in front-end development and full-stack development, working heavily with JavaScript. He is an avid conference speaker and teacher, presenting on web development topics. He is passionate about front-end development and its future, now taking that passion to the world of Elm.