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)

More ways to filter data


In RxJS, we also have other operators to filter data. In this section, we will learn about the following operators:

  • first()
  • take()
  • takeLast()
  • takeWhile()
  • skip()
  • skipWhile()

We can use these operators when we are interested only in a subset of data from an observable.

Note

There are other operators to filter data on RxJS but these are the most common ones.

The first() operator

The first() operator returns a new observable containing only the first element in an observable which satisfies a given condition. This operator has the following signature:

observable.first([condition],[context],[defaultValue]); 

All parameters are optional:

  • condition: This is the function which the value must satisfy to be retrieved
  • context: This is an argument used in the given conditional function
  • defaultValue: This is a value used as the default if the observable is exhausted and no item satisfies the given condition

If no condition is supplied, this operator returns the first element in the Observable...