Book Image

Node.js Web Development - Fourth Edition

By : David Herron
Book Image

Node.js Web Development - Fourth Edition

By: David Herron

Overview of this book

Node.js is a server-side JavaScript platform using an event-driven, non-blocking I/O model allowing users to build fast and scalable data-intensive applications running in real time. This book gives you an excellent starting point, bringing you straight to the heart of developing web applications with Node.js. You will progress from a rudimentary knowledge of JavaScript and server-side development to being able to create, maintain, deploy and test your own Node.js application.You will understand the importance of transitioning to functions that return Promise objects, and the difference between fs, fs/promises and fs-extra. With this book you'll learn how to use the HTTP Server and Client objects, data storage with both SQL and MongoDB databases, real-time applications with Socket.IO, mobile-first theming with Bootstrap, microservice deployment with Docker, authenticating against third-party services using OAuth, and use some well known tools to beef up security of Express 4.16 applications.
Table of Contents (19 chapters)
Title Page
Dedication
Packt Upsell
Contributors
Preface
Index

Sending and receiving events with EventEmitters


EventEmitters are one of the core idioms of Node.js. If Node.js's core idea is an event-driven architecture, emitting events from an object is one of the primary mechanisms of that architecture. An EventEmitter is an object that gives notifications—events—at different points in its life cycle. For example, an HTTP Server object emits events concerning each stage of the startup/shutdown of the Server object, and as HTTP requests are made from HTTP clients.

Many core Node.js modules are EventEmitters, and EventEmitters are an excellent skeleton to implement asynchronous programming. EventEmitters have nothing to do with web application development, but they are so much part of the Node.js woodwork that you may skip over their existence. 

In this chapter, we'll work with the HTTPServer and HTTPClient objects. Both are subclasses of the EventEmitter class, and rely on it to send events for each step of the HTTP protocol. 

JavaScript classes and class...