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 map() operator

The map() operator is common when working with arrays or any other kinds of sequences in functional languages and frameworks. In JavaScript, array objects have a method called map(). This method is available in all modern browsers now.

The map() operator calls the provided function once for each element in the Observable. This function takes the object in the Observable as input and returns another object. So the Observable returned by the map() operator will propagate the result of calling the map function for each element of the original Observable.

The provided function is called as soon as the object is propagated by the original Observable; it is called in the same order.

So the map() operator has the following signature:,[thisContext]); 

The first parameter is mandatory and the second is optional:

  • mapFunction: This is a function that takes an element of the observable as input and returns another object to be propagated instead
  • thisContext: This...