Flapjax: a programming language for Ajax applications. Flapjax is a new programming language designed around the demands of modern, client-based Web applications. Its principal features include: Event-driven, reactive evaluation; An event-stream abstraction for communicating with web services; Interfaces to external web services. Flapjax is easy to learn: it is just a JavaScript framework. Furthermore, because Flapjax is built entirely atop JavaScript, it runs on traditional Web browsers without the need for plug-ins or other downloads. It integrates seamlessly with existing JavaScript code and other frameworks.