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

Our problem – doing something only once

Let's consider a simple but common situation. You have developed an e-commerce site; the user can fill their shopping cart, and in the end, they must click on a Bill me button so their credit card will be charged. However, the user shouldn't click twice (or more) or they will be billed several times.

The HTML part of your application might have something like this somewhere:

<button id="billButton" onclick="billTheUser(some, sales, data)">Bill me</button>

And, among the scripts, you'd have something similar to the following code:

function billTheUser(some, sales, data) {
window.alert("Billing the user...");
// actually bill the user
Assigning the events handler directly in HTML, the way I did it, isn't recommended. Rather, unobtrusively, you should assign the...