Book Image

Professional JavaScript

By : Hugo Di Francesco, Siyuan Gao, Vinicius Isola, Philip Kirkbride
Book Image

Professional JavaScript

By: Hugo Di Francesco, Siyuan Gao, Vinicius Isola, Philip Kirkbride

Overview of this book

In depth knowledge of JavaScript makes it easier to learn a variety of other frameworks, including React, Angular, and related tools and libraries. This book is designed to help you cover the core JavaScript concepts you need to build modern applications. You'll start by learning how to represent an HTML document in the Document Object Model (DOM). Then, you'll combine your knowledge of the DOM and Node.js to create a web scraper for practical situations. As you read through further lessons, you'll create a Node.js-based RESTful API using the Express library for Node.js. You'll also understand how modular designs can be used for better reusability and collaboration with multiple developers on a single project. Later lessons will guide you through building unit tests, which ensure that the core functionality of your program is not affected over time. The book will also demonstrate how constructors, async/await, and events can load your applications quickly and efficiently. Finally, you'll gain useful insights into functional programming concepts such as immutability, pure functions, and higher-order functions. By the end of this book, you'll have the skills you need to tackle any real-world JavaScript development problem using a modern JavaScript approach, both for the client and server sides.
Table of Contents (12 chapters)

Function Composition

Function composition is another concept that leaks over from mathematics.

Given two functions, a and b, compose returns a new function that applies a to the output of b, which is then applied to a given set of parameters.

Function composition is a way to create a complex function from a set of smaller ones.

This will mean you might end up with a bunch of simple functions that do one thing well. Functions with a single purpose are better at encapsulating their functionality and therefore help with separation of concerns.

Composing functions ties in with currying and the partial application of functions since currying/partial application is a technique that allows you to have specialized versions of generic functions, like so:

const sum = x => y => x + y;
const multiply = x => y => x * y;
const compose = (f, g) => x => f(g(x));
const add1 = sum(1);
const add2 = sum(2);
const double = multiply(2);

To explain the following code...