A hands on approach to learning ReasonML from the perspective of a web developer. Key Features Hands on learning by building a real world app shell that includes client-side routing and more. Understand Reason's ecosystem including BuckleScript and various npm workflows. Learn how Reason differs from TypeScript and Flow, and how to use it to make refactoring less stressful. Book DescriptionReasonML, also known as Reason, is a new syntax and toolchain for OCaml that was created by Facebook and is meant to be approachable for web developers. Although OCaml has several resources, most of them are from the perspective of systems development. This book, alternatively, explores Reason from the perspective of web development. You'll learn how to use Reason to build safer, simpler React applications and why you would want to do so. Reason supports immutability by default, which works quite well in the context of React. In learning Reason, you will also learn about its ecosystem - BuckleScript, JavaScript interoperability, and various npm workflows. We learn by building a real-world app shell, including a client-side router with page transitions, that we can customize for any Reason project. You'll learn how to leverage OCaml's excellent type system to enforce guarantees about business logic, as well as preventing runtime type errors.You'll also see how the type system can help offload concerns that we once had to keep in our heads. We'll explore using CSS-in-Reason, how to use external JSON in Reason, and how to unit-test critical business logic. By the end of the book, you'll understand why Reason is exploding in popularity and will have a solid foundation on which to continue your journey with Reason. What you will learn Learn why Reason is exploding in popularity and why it's the future of React Become familiar with Reason's syntax and semantics Learn about Reason's ecosystem: BuckleScript and JavaScript interoperability Learn how to build React applications with Reason Learn how to use Reason's type system as a tool to provide amazing guarantees Gain a solid foundation on which to continue your journey Who this book is forThe target audience of this book is web developers who are somewhat familiar with ReactJS and who want to learn why ReasonML is the future of ReactJS.