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

A functional solution

Let's try to be more general: after all, requiring that some function or other be executed only once, isn't that outlandish, and may be required elsewhere! Let's lay down some principles:

  • The original function (the one that may be called only once) should do that thing, and no other
  • We don't want to modify the original function in any way
  • We need to have a new function that will call the original one only once
  • We want a general solution that we can apply to any number of original functions


The first principle listed previously is the single responsibility principle (the S in S.O.L.I.D.), which states that every function should be responsible over a single functionality. For more on S.O.L.I.D., check the article by Uncle Bob (Robert C. Martin, who wrote the five principles) at

Can we do it? Yes; and we'll write a higher-order function, which we'll be able to apply to any function, to produce a new function that...