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


11.1. Decorating methods, the future way. In Chapter 6, Producing Functions - Higher-Order Functions, we wrote a decorator to enable logging for any function. Currently, method decorators are being considered for upcoming versions of JavaScript: refer to for that (Draft 2 means that inclusion of this feature in the standard is likely, although there may be some additions or small changes). Study the draft and take a look at what makes the next code tick.

Some questions: Do you see the need for the savedMethod variable? Why do we use function() when assigningnew descriptor.value, instead of an arrow function? Can you understand why .bind() is used? What is descriptor?

const logging = (target, name, descriptor) => {
    const savedMethod = descriptor.value;
    descriptor.value = function(...args) {
        console.log(`entering ${name}: ${args}`);
        try {
            const valueToReturn = savedMethod.bind(this)(...args);