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

Altering functions

In the previous section, we considered some ways of wrapping functions, so they would maintain their original functionality, though enhanced in some ways. Now we'll turn to actually modifying what the functions do, so the new results will actually differ from the original function's ones.

Doing things once, revisited

Back in Chapter 2, Thinking Functionally - A First Example, we went through an example of developing an FP-style solution for a simple problem: fixing things so a given function would work only once:

const once = func => {
    let done = false;
    return (...args) => {
        if (!done) {
            done = true;

This is a perfectly fine solution, and we have nothing to object to. We can, however, think of a variation. We could observe that the given function gets called once, but its return value gets lost. That's easy to fix, however; all we require is adding a return statement. However, that wouldn't be...