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)


Middleware functions in Express are functions that run before the function associated with an endpoint. Some common examples of this include logging a request or checking for authentication before running the main function of an endpoint. In these cases, the logging and authentication functions will be common among all the endpoints that use them. By using middleware, we can reuse code that is common across endpoints.

With Express, we can have middleware functions that run for all endpoints by using app.use(). For example, if we wanted to create a function that logs a request to the console before running the main route, we could write a logger middleware:

var logger = function (req, res, next) {
  // Request is logged
  // Call the special next function which passes the request to next function

To have the logger run with all endpoints, we tell our app to use it with the following: