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)

RxJS Subjects

Subjects could be both an Observable and an Observer. They can be seen as a pushable Observable; they let you add more data to be propagated through them.

Subjects expose three important methods: onNext(), onError(), and onCompleted(). These methods can be used to send events through the observable sequence. You can see their usage in the following example:

var subject = new Rx.Subject(); 

    (message)=> console.log(message), 
    (err)=>console.log('An error happened: '+err.message), 

subject.onNext('Hello World!!!'); 

In this example, we created a new subject and subscribed to it, using the subscribe() method. Then, we pushed data on this subject using the onNext() method, and we finally finished it calling the onCompleted() method.

If you run this code, you will see the following output:

    Hello World!!!

We can also propagate an error through a subject using its onError() method: