Book Image

Mastering Reactive JavaScript

By : Erich de Souza Oliveira
Book Image

Mastering Reactive JavaScript

By: Erich de Souza Oliveira

Overview of this book

If you’re struggling to handle a large amount of data and don’t know how to improve your code readability, then reactive programming is the right solution for you. It lets you describe how your code behaves when changes happen and makes it easier to deal with real-time data. This book will teach you what reactive programming is, and how you can use it to write better applications. The book starts with the basics of reactive programming, what Reactive Extensions is, and how can you use it in JavaScript along with some reactive code using Bacon. Next, you’ll discover what an Observable and an Observer are and when to use them.You'll also find out how you can query data through operators, and how to use schedulers to react to changes. Moving on, you’ll explore the RxJs API, be introduced to the problem of data traffic (backpressure), and see how you can mitigate it. You’ll also learn about other important operators that can help improve your code readability, and you’ll see how to use transducers to compose operators. At the end of the book, you’ll get hands-on experience of using RxJs, and will create a real-time web chat using RxJs on the client and server, providing you with the complete package to master RxJs.
Table of Contents (11 chapters)

Reacting to changes

As discussed earlier, an observable is an object where you can listen to events. The act of listening to events in this object is called subscription. Here, we will see the different ways in which we can subscribe to an observable and also how we can stop listening to events in this observable (unsubscribe).


We call subscribing to an observable an act of adding a function to be called when an event happens. Using bacon.js, we can be notified when a value is emitted (the onValue(), log(), and assign() methods), when an error has occurred (the onError() method), or when our observable is closed (at the end).

Subscribing using the onValue() method

The most common way of subscribing to an observable is using the onValue() method. This method has the following signature:


So let's subscribe to eventStream to log every event on this stream, as follows: