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)

Concatenating observables


RxJS enables some operators to combine several observables in a single one containing the events from all, the most common operators are concat() and merge(), which simply creates a new observable containing all data from the others, but in this chapter we will also learn how to do more interesting combinations with other operators.

Using the concat() operator

The most common operator to concatenate two sources of data (observables) is the concat() operator. This operator receives multiple observables as arguments and concatenates all observables from the left to right. It preserves the order of the elements in the observables and only propagates data from the next observable if the current one is already terminated.

This operator has the following signature:

observable.concat(observables); 

It accepts any number of arguments, but they all must be observables:

  • observable: It is any number of observables

The easiest possible example is to use it to combine two observables...