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)

The flatMap() operator

In the previous section, we saw the map() operator and how we can use it to map an object into another object in an observable. The flatMap() operator works similarly. It receives a function as a parameter. The function provided as argument must returns an Observable, and the elements of this Observable is propagated instead.

This operator may seen a little bit confusing, but there is another way to understand it. The flatMap() operator runs the given function for each element in the original array. It creates an Observable that will emit each piece of data coming out from other Observables keeping the order.

The flatMap() operator is illustrated in the following signature:


The first parameter is mandatory and the second is optional:

  • flatMapFunction: This is a function that takes an element of the observable as input and returns another observable whose elements are going to be propagated instead
  • thisContext: This is any...