Book Image

Mastering JavaScript Functional Programming

By : Federico Kereki
Book Image

Mastering JavaScript Functional Programming

By: Federico Kereki

Overview of this book

Functional programming is a programming paradigm for developing software using functions. Learning to use functional programming is a good way to write more concise code, with greater concurrency and performance. The JavaScript language is particularly suited to functional programming. This book provides comprehensive coverage of the major topics in functional programming with JavaScript to produce shorter, clearer, and testable programs. You’ll delve into functional programming; including writing and testing pure functions, reducing side-effects, and other features to make your applications functional in nature. Specifically, we’ll explore techniques to simplify coding, apply recursion for loopless coding, learn ways to achieve immutability, implement design patterns, and work with data types. By the end of this book, you’ll have developed the JavaScript skills you need to program functional applications with confidence.
Table of Contents (22 chapters)
Title Page
About the Author
About the Reviewer
Customer Feedback
Connecting Functions - Pipelining and Composition
Answers to Questions

Chapter 10. Ensuring Purity - Immutability

In Chapter 4, Behaving Properly - Pure Functions, when we considered pure functions and their advantages, we saw that side-effects such as modifying a received argument or a global variable were frequent causes for impurity. Now, after several chapters dealing with many aspects and tools of FP, let's get to the concept of immutability: how to work with objects in such a way that accidentally modifying them will become harder or, even better, impossible.

We cannot force developers to work in a safe, guarded way, but if we find some way to make data structures immutable (meaning that they cannot be directly changed, except through some interface that never allows modifying the original data, but produces new objects instead) then we'll have an enforceable solution. In this chapter, we will see two distinct approaches to working with such immutable objects and data structures:

  • Basic JS ways, such as freezing objects, plus cloning to create new ones instead...