Why do I need it?

Functional reactive programming is especially useful when implementing one of these scenarios:

• Graphical user interface
• Animation
• Robotics
• Simulation
• Computer vision

A few years ago, all a user could do in a web app was fill a form with some data and post it to a server. Nowadays our web apps and mobile apps present to the user a richer interface, empowering them with real-time information and giving a lot more interaction possibilities. So, as the applications evolved, we needed more tools to achieve the new requirements.

Using it you can abstract the source of your data to the business logic of your application–this lets you write more concise and decoupled code, improves the reuse, and leads to a more testable code as you can easily mock your streams to test your business logic.

In this book we will use Reactive Extensions to explain and implement an example reactive application. Reactive Extensions are widely used in the industry and they have implementations for different languages (.Net, Scala, JavaScript, Ruby, Java, and so on) so you can easily translate the things you learn in this book to other languages.

In my personal opinion, Reactive Extensions have some concepts which are hard to understand for those unfamiliar with reactive programming. For this reason, we will learn the basics using a more simple library (bacon.js), and as soon as you understand the basics and the concepts, I will give you more tools using RxJS.