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

Assert – the basis of testing methodologies


Node.js has a useful built-in testing tool, the assert module. Its functionality is similar to assert libraries in other languages. Namely, it's a collection of functions for testing conditions, and if the conditions indicate an error, the assert function throws an exception.

At its simplest, a test suite is a series of assert calls to validate the behavior of a thing being tested. For example, a test suite could instantiate the user authentication service, then make an API call, using assert methods to validate the result, then make another API call, validating its results, and so on.

Consider a code snippet like this, which you could save in a file named deleteFile.js:

const fs = require('fs'); 

exports.deleteFile = function(fname, callback) { 
  fs.stat(fname, (err, stats) => { 
    if (err) callback(new Error(`the file ${fname} does not exist`)); 
    else { 
      fs.unlink(fname, err2 => { 
        if (err) callback(new Error(`could not...