Book Image

Mastering JavaScript Functional Programming - Second Edition

By : Federico Kereki
Book Image

Mastering JavaScript Functional Programming - Second Edition

By: Federico Kereki

Overview of this book

Functional programming is a paradigm for developing software with better performance. It helps you write concise and testable code. To help you take your programming skills to the next level, this comprehensive book will assist you in harnessing the capabilities of functional programming with JavaScript and writing highly maintainable and testable web and server apps using functional JavaScript. This second edition is updated and improved to cover features such as transducers, lenses, prisms and various other concepts to help you write efficient programs. By focusing on functional programming, you’ll not only start to write but also to test pure functions, and reduce side effects. The book also specifically allows you to discover techniques for simplifying code and applying recursion for loopless coding. Gradually, you’ll understand how to achieve immutability, implement design patterns, and work with data types for your application, before going on to learn functional reactive programming to handle complex events in your app. Finally, the book will take you through the design patterns that are relevant to functional programming. By the end of this book, you’ll have developed your JavaScript skills and have gained knowledge of the essential functional programming techniques to program effectively.
Table of Contents (17 chapters)
Technical Requirements

Testing – pure versus impure

We have seen how pure functions are conceptually better than impure ones, but we cannot set out on a crusade to vanquish all impurity from our code. First, no one can deny that side effects can be useful, or at least unavoidable: you will need to interact with the DOM or call a web service, and there are no ways to do this in a pure way. So, rather than bemoaning the fact that you have to allow for impurity, try to structure your code so that you can isolate the impure functions and let the rest of your code be the best it can possibly be.

With this in mind, you'll have to be able to write unit tests for all kinds of functions, pure or impure. Writing unit tests for functions is different, in terms of both their difficulty and complexity than dealing with pure or impure functions. While coding tests for the former is usually quite...