Want to simplify web development? This hands-on book shows you how to write frontend and backend code simultaneously, using the Opa framework. Opa provides a complete stack for web application development, including a web server, database engine, distribution libraries, and a programming language that compiles to JavaScript. You'll learn step-by-step how to use Opa by building two projects through the course of the book: a wiki application similar to Wikipedia, and a Twitter-like micro-blogging platform. Discover how easy it is to use Opa to develop applications with real-time updates, database interactions, and web service design. Learn fundamental concepts, including Opa's functional programming style Discover how Opa compiles to JavaScript, using jQuery on the frontend and Node.js on the server Construct HTML resources dynamically and embed static resources on an Opa server Use Opa's method for performing CRUD operations and storing key-value pairs in MongoDB Build an Opa user interface with the Bootstrap toolkit from Twitter Learn variant types, pattern-matching, polymorphic types, recursive functions, and other advanced features Manage user accounts by building login forms, handling account activation, and tracking logged users Build a reactive UI - a real-time interface that continuously updates user events