Learning Node.js Development E-Book

Andrew Mead

• Herausgeber: Packt Publishing
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 589

Veröffentlichungsjahr: 2018

Beschreibung

A comprehensive, easy-to-follow guide to creating complete Node apps and understanding how to build, deploy, and test your own apps.

Key Features

• Entirely project-based and practical
• Explains the "Why" of Node.js features, not just the "how", providing you with a deep understanding and enabling you to easily apply concepts in your own applications
• Covers the full range of technologies around Node.js – NPM, version control with Git, and much more

Book Description

Learning Node.js Development is a practical, project-based book that provides you with all you need to get started as a Node.js developer. Node is a ubiquitous technology on the modern web, and an essential part of any web developers' toolkit. If you are looking to create real-world Node applications, or you want to switch careers or launch a side project to generate some extra income, then you're in the right place. This book has been written around a single goal—turning you into a professional Node developer capable of developing, testing, and deploying real-world production applications.

Learning Node.js Development is built from the ground up around the latest version of Node.js (version 9.x.x). You'll be learning all the cutting-edge features available only in the latest software versions.

This book cuts through the mass of information available around Node and delivers the essential skills that you need to become a Node developer. It takes you through creating complete apps and understanding how to build, deploy, and test your own Node apps. It maps out everything in a comprehensive, easy-to-follow package designed to get you up and running quickly.

What you will learn

• Learn the fundamentals of Node
• Build apps that respond to user input
• Master working with servers
• Learn how to test and debug applications
• Deploy and update your apps in the real world
• Create responsive asynchronous web applications

Who this book is for

This book targets anyone looking to launch their own Node applications, switch careers, or freelance as a Node developer. You should have a basic understanding of JavaScript in order to follow this course.

Andrew Mead is a full-stack developer living in beautiful Philadelphia! He launched his first Udemy course in 2014 and had a blast teaching and helping others. Since then, he has launched 3 courses with over 21,000 students and over 1,900 5-star reviews. Andrew currently teaches Node, Gulp, and React. Before he started teaching, he created a web app development company. He has helped companies of all sizes launch production web applications to their customers. He has had the honor of working with awesome companies such as Siemens, Mixergy, and Parkloco. He has a Computer Science degree from Temple University, and he has been programming for just over a decade. He loves creating, programming, launching, learning, teaching, and biking.

Leseprobe

Learning Node.js Development

Learn the fundamentals of Node.js, and deploy and test Node.js applications on the web

Andrew Mead

BIRMINGHAM - MUMBAI

Learning Node.js Development

Copyright © 2018 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing or its dealers and distributors, will be held liable for any damages caused or alleged to have been caused directly or indirectly by this book.

Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

Acquisition Editor:Ben Renow-ClarkeContent Development Editor:Monika SangwanTechnical Editors: Anupam Tiwari, Gaurav GavasCopy Editors:Safis Editing, Tom JacobProject Editor:Suzanne CoutinhoProofreader:Safis EditingIndexer:Pratik ShirodkarProduction Coordinator:Nilesh Mohite

First published: January 2018

Production reference: 1300118

Published by Packt Publishing Ltd. Livery Place 35 Livery Street Birmingham B3 2PB, UK.

ISBN 978-1-78839-554-0

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Contributor

About the author

Andrew Mead is a full-stack developer living in beautiful Philadelphia! He launched his first Udemy course in 2014 and had a blast teaching and helping others. Since then, he has launched 3 courses with over 21,000 students and over 1,900 5-star reviews.

Andrew currently teaches Node, Gulp, and React. Before he started teaching, he created a web app development company. He has helped companies of all sizes launch production web applications to their customers. He has had the honor of working with awesome companies such as Siemens, Mixergy, and Parkloco. He has a Computer Science degree from Temple University, and he has been programming for just over a decade. He loves creating, programming, launching, learning, teaching, and biking.

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Table of Contents

Preface

Who this book is for

What this book covers

To get the most out of this book

Download the example code files

Conventions used

Get in touch

Reviews

Getting Set Up

Node.js installation

Node.js version confirmation

Installing Node

Verifying installation

What is Node?

Differences between JavaScript coding using Node and in the browser

Why use Node

Blocking and non-blocking software development

The working of blocking I/O

The working non-blocking I/O

Blocking and non-blocking examples using Terminal

Node community – problem solving open source libraries

Different text editors for node applications

Hello World – creating and running the first Node app

Creating the Node application

Running the Node application

Summary

Node Fundamentals – Part 1

Module basics

Using case for require()

Initialization of an application

The built-in module to use require()

Creating and appending files in the File System module

The OS module in require()

Concatenating user.username

Using template strings

Require own files

Making a new file to load other files

Exporting files from note.js to use in app.js

A simple example of the working of the exports object

Exporting the functions

Exercise – adding a new function to the export object

Solution to the exercise

Third-party modules

Creating projects using npm modules

Installing the lodash module in our app

Installation of lodash

Using the utilities of lodash

Using the _.isString utility

Using _.uniq

The node_modules folder

Global modules

Installing the nodemon module

Executing nodemon

Getting input

Getting input from the user inside the command line

Accessing the command-line argument for the notes application

Adding if/else statements

Exercise – adding two else if clauses to an if block

Solution to the exercise

Getting the specific note information

Summary

Node Fundamentals – Part 2

yargs

Installing yargs

Running yargs

Working with the add command

Working with the list command

The read command

Dealing with the errors in parsing commands

The remove command

Fetching command

JSON

Converting objects into strings

Defining a string and using in app as an object

Converting a string back to an object

Storing the string in a file

Writing the file in the playground folder

Reading out the content in the file

Adding and saving notes

Adding notes

Adding notes to the notes array

Fetching new notes

Trying and catching code block

Making the title unique

Refactoring

Moving functionality into individual functions

Working with fetchNotes

Working with saveNotes

Testing the functionality

Summary

Node Fundamentals – Part 3

Removing a note

Using the removeNote function

Printing a message of removing notes

Reading note

Using the getNote function

Running the getNote function

The DRY principle

Using the logNote function

Debugging

Executing a program in debug mode

Working with debugging

Using debugger inside the notes application

Listing notes

Using the getAll function

Advanced yargs

Using chaining syntax on yargs

Calling the .help command

Adding the options object

Adding the title

Adding the body

Adding support to the read and remove commands

Adding the titleOption and bodyOption variables

Testing the remove command

Arrow functions

Using the arrow function

Exploring the difference between regular and arrow functions

Exploring the arguments array

Summary

Basics of Asynchronous Programming in Node.js

The basic concept of asynchronous program

Illustrating the async programming model

Call stack and event loop

A synchronous program example

The call stack

Running the synchronous program

A complex synchronous program example

An async program example

The Node API in async programming

The callback queue in async programming

The event loop

Running the async code

Callback functions and APIs

The callback function

Creating the callback function

Running the callback function

Simulating delay using setTimeout

Making request to Geolocation API

Using Google Maps API data in our code

Installing the request package

Using request as a function

Running the request

Pretty printing objects

Using the body argument

Making up of the HTTPS requests

The response object

The error argument

Printing data from the body object

Printing the formatted address

Printing latitude and longitude

Summary

Callbacks in Asynchronous Programming

Encoding user input

Installing yargs

Configuring yargs

Printing the address to screen

Encoding and decoding the strings

Encoding URI component

Decoding URI component

Pulling the address out of argv

Callback errors

Checking error in Google API request

Adding the if statement for callback errors

Adding if else statement to check body status property

Testing the body status property

Abstracting callbacks

Refactoring app.js and code into geocode.js file

Working on request statement

Creating geocode file

Adding callback function to geocodeAddress

Setting up the function in geocodeAddress function in app.js

Implementing the callback function in geocode.js file

Testing the callback function in geocode.js file

Wiring up weather search

Exploring working of API in the browser

Exploring the actual URL for code

Making a request for the weather app using the static URL

Error handling in the the callback function

Another way of error handling

Testing the error handling in callback

Chaining callbacks together

Refactoring our request call in weather.js file

Defining the new function getWeather in weather file

Providing weather directory in app.js

Passing the arguments in the getWeather function

Printing errorMessage in the getWeather function

Implementing getWeather callback inside weather.js file

Adding dynamic latitude and longitude

Changing console.log calls into callback calls

Chaining the geocodeAddress and getWeather callbacks together

Moving getWeather call into geocodeAddress function

Replacing static coordinates with dynamic coordinates

Testing the chaining of callbacks

Summary

Promises in Asynchronous Programming

Introduction to ES6 promises

Creating an example promise

Calling the promise method then

Running the promise example in Terminal

Error handling in promises

Merits of promises

Advanced promises

Providing input to promises

Returning the promises

Promise chaining

Error handling in promises chaining

The catch method

The request library in promises

Testing the request library

Weather app with promises

Fetching weather app code from the app.js file

Axios documentations

Installing axios

Making calls in the app-promise file

Making axios request

Error handling in axios request

Error handling with ZERO_RESULT body status

Generating the weather URL

Chaining the promise calls

Summary

Web Servers in Node

Introducing Express

Configuring Express

Express docs website

Installing Express

Creating an app

Exploring the developer tools in the browser for the app request

Passing HTML to res.send

Sending JSON data back

Error handling in the JSON request

The static server

Making an HTML page

The head tag

The body tag

Serving the HTML page in the Express app

The call to app.listen

Rendering templates

Installing the hbs module

Configuring handlebars

Our first template

Getting the static page for rendering

Injecting data inside of templates

Rendering the template for the root of the website

Advanced templates

Adding partials

Working of partial

The Header partial

The Handlebars helper

Arguments in Helper

Express Middleware

Exploring middleware

Creating a logger

Printing message to file

The maintenance middleware without the next object

Testing the maintenance middleware

Summary

Deploying Applications to Web

Adding version control

Installing Git

Git on macOS

Git on Windows

Testing the installation

Turning the node-web-server directory into a Git repository

Using Git

Adding untracked files to commit

Making a commit

Setting up GitHub and SSH keys

Setting up SSH keys

SSH keys documentations

Working on commands

Generating a key

Starting up the SSH agent

Configuring GitHub

Testing the configuration

Creating a new repository

Setting up the repository

Deploying the node app to the Web

Installing Heroku command-line tools

Log in to Heroku account locally

Getting SSH key to Heroku

Setting up in the application code for Heroku

Changes in the server.js file

Changes in the package.json file

Making a commit in Heroku

Running the Heroku create command

Summary

Testing the Node Applications – Part 1

Basic testing

Installing the testing module

Testing a Node project

Mocha – the testing framework

Creating a test file for the add function

Creating the if condition for the test

Testing the squaring a number function

Autorestarting the tests

Using assertion libraries in testing Node modules

Exploring assertion libraries

Chaining multiple assertions

Multiple assertions for the square function

Exploring usage of expect with bogus test

Using toBe and toNotBe to compare array/objects

Using the toEqual and toNotEqual assertions

Using toInclude and toExclude

Testing the setName method

The asynchronous testing

Creating the asyncAdd function using the setTimeout object

Writing the test for the asyncAdd function

Making assertion for the asyncAdd function

Adding the done argument

The asynchronous testing for the square function

Creating the async square function

Writing test for asyncSquare

Making assertions for the asyncSquare function

Summary

Testing the Node Applications – Part 2

Testing the Express application

Setting up testing for the Express app

Testing the Express app using SuperTest

The SuperTest documentation

Creating a test for the Express app

Writing the test for the Express app

Testing our first API request

Setting up custom status

Adding flexibility to SuperTest

Creating an express route

Writing the test for the express route

Organizing test with describe()

Adding describe() for individual methods

Adding the route describe block for the server.test.js file

Test spies

Creating a test file for spies

Creating a spy

Setting up spies assertions

More details out of spy assertion

Swapping of the function with spy

Installing and setting up the rewire function

Replacing db with the spy

Writing a test to verify swapping of the function

Summary

Conclusion

Another Book You May Enjoy

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Preface

Welcome to Learning Node.js Development. This book is packed with a ton of content, projects, challenges and real-world examples, all designed to teach you Node by doing. This means you'll be getting your hands dirty early on in the upcoming chapters writing some code, and you'll be writing code for every project. You will be writing every line of code that powers our applications. Now, we would require a text editor for this book. We have various text editor options that you can use. I always recommend using Atom, which you can find at atom.io. It's free, open-source, and it's available for all operating systems, namely Linux, macOS, and Windows. It's created by the folks behind GitHub.

All the projects in the book are fun to build and they were designed to teach you everything required to launch your own Node app, from planning to development and testing to deploying. Now, as you launch these different Node applications and move through the book, you will run into errors, which is bound to happen. Maybe something doesn't get installed as expected, or maybe you try to run an app and instead of getting the expected output, you get a really long obscure error message. Don't worry, I am there to help. I'll show you tips and tricks to get pass through those errors in the chapters. Let's go ahead and get to it.

Who this book is for

This book targets anyone looking to launch their own Node applications, switch careers, or freelance as a Node developer. You should have a basic understanding of JavaScript in order to follow this book.

What this book covers

Chapter 1, Getting Set Up, talks about what Node is and why you want to use it. In this chapter, you'll learn Node installation and by the end of the chapter, you'll be able to run your first Node application.

Chapter 2, Node Fundamentals - Part 1, talks about building Node applications. The Node Fundamentals topic has been divided into 3 parts. Part 1 of this topic includes module basics, requiring own files, and third-party NPM modules. 

Chapter 3, Node Fundamentals - Part 2, continues our discussion on some more Node fundamentals. This chapter explores yargs, JSON, the addNote function, and refactor, moving functionality into individual  functions and testing the functionality. 

Chapter 4, Node Fundamentals - Part 3, includes things such as read and write from the file system. We'll look into advanced yargs configuration, debugging broken apps, and some new ES6 functions.

Chapter 5, Basics of Asynchronous Programming in Node.js, covers basic concepts, terms, and technologies related to the async programming, making it super-practical and using it in our weather application. 

Chapter 6, Callbacks in Asynchronous Programming, is the second part of async programming in Node. We'll look into callbacks, HTTPS requests, and error handling inside of our callback functions. We'll also look into the forecast API and fetching real-time weather data for our address.

Chapter 7, Promises in Asynchronous Programming, is the third and last part of async programming in Node. This chapter focuses on Promises, how it works, why they are useful, and so on. At the end of this chapter, we'll use Promises in our weather app.

Chapter 8, Web Servers in Node, talks about Node web servers and integrating version control into Node applications. We'll also introduce a framework called Express, one of the most important NPM libraries. 

Chapter 9, Deploying Applications to Web, talks about deploying the applications to the Web. We'll be using Git, GitHub, and deploy our live app to the Web using these two services. 

Chapter 10, Testing the Node Applications- Part 1, talks about how we can test our code to make sure it is working as expected. We'll work on setting up for testing and then writing our test cases. We'll look into the basic testing framework and asynchronous testing. 

Chapter 11, Testing the Node Application - Part 2, continues our journey of testing Node applications. In this chapter, we'll work on testing the Express applications and look into some advanced methods of testing.

To get the most out of this book

A web browser, we'll be using Chrome throughout the course book but any browser will do, and Terminal, sometimes known as the command line on Linux or the Command Prompt on Windows. Atom as the text editor. The following list of modules will be used throughout the course of this book:

lodash

nodemon

yargs

request

axios

express

hbs

heroku

rewire

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Getting Set Up

In this chapter, you'll get your local environment set up for the rest of the book. Whether you're on macOS, Linux, or Windows, we'll install Node and look at exactly how we can run Node applications.

We'll talk about what Node is, why you would ever want to use it, and why you would want to use Node as opposed to something like Rails, C++, Java, or any other language that can accomplish similar tasks. By the end of this chapter, you will be running your very first Node application. It's going to be simple, but it is going to get us to the path to creating real-world production Node apps, which is the goal of this book.

More specifically, we'll cover the following topics:

Node.js installation

What Node is

Why use Node

Atom

Hello World

Node.js installation

Before we start talking about what Node is and why it's useful, you need to first install Node on your machine, because in the next couple of sections, we'll want to run a little bit of Node code.

Now, to get started, we just need two programs—a browser, I'll be using Chrome throughout the book, but any browser will do, and Terminal. I'll use Spotlight to open up Terminal, which is what it's known as on my operating system.

If you're on Windows, look for the Command Prompt, you can search using the Windows key and then by typing command prompt, and on Linux, you're looking for the command line, although depending on your distribution it might be called Terminal or Command Prompt.

Now, once you have that program open, you'll see a screen, as shown in the following screenshot:

Essentially, it's waiting for you to run a command. We'll run quite a few commands from Terminal throughout the book. I'll discuss it in a few sections later, so if you've never used this before, you can start navigating comfortably.

Node.js version confirmation

In the browser, we can head over to nodejs.org to grab the installer for the latest version of Node(as shown here). In this book, we'll use the most recent version, version 9.3.0:

It is important that you install a V8 version of Node.js. It doesn't have to be 4.0, it could be 1.0, but it is important it's on that V8 branch, because there is a ton of new features that come along with V8, including all of the features you might have come to love in the browser using ES6.

ES6 is the next version of JavaScript and it comes with a lot of great enhancements we'll be using throughout the book. If you look at the following image,Node.js Long Term Support Release Schedule(https://github.com/nodejs/LTS), you can see that the current Node version is V8, out in April 2017:

Before going further, I would like to talk about the Node release cycle. What I have in the preceding image is the official release cycle, this is released by Node. You'll notice that only next to the even Node numbers do you find the active LTS, the blue bar, and the maintenance bar. Now, LTS stands for long-term support, and this is the version that's recommended for most users. I'd recommend that you stick with the currently offered LTS option (Node v 8.9.4 LTS), though anything on the left-hand side will do, this is shown as the two green buttons on nodejs.org.

Now, as you can see, the major version numbers, bump every six months. Regardless of any sort of big overarching change, this happens like clockwork even if nothing drastic has changed. It's not like Angular where jumping from 1.0 to 2.0 was almost like using a completely different library. This is just not the case with Node, what you're getting from this book is the latest and greatest Node has to offer.

Installing Node

Once the version is confirmed and selected, all we have to do is to click the required version button on the Node website (nodejs.org) and download the installer. The installer is one of those basic click Next a few times and you're done type of installers, there's no need to run any fancy commands. I'll start the installer. As shown in the followingscreenshot, it'll just ask a few questions, then let's click onNextorContinuethrough all of them:

You might want to specify a custom destination, but if you don't know what that means, and you don't usually do it when installing programs, skip that step too. Here, in the nextscreenshot, you can see that I'm using just 58.6 MB, no problem.

I'll run the installer by entering my password. And once I enter my password, it should really only take a couple of seconds to get Node installed:

As shown in the followingscreenshot, we have a message that saysThe installation was completed successfully, which means we are good to go:

Verifying installation

Now that Node has been installed successfully, we can go ahead and verify that by running Node from Terminal. Inside Terminal, I'll shut it down by going to Quit Terminal and open it up again:

The reason I'm opening it up is because we've installed a new command, and some Terminals require a restart before they will be able to run that new command.

In our case, we restarted things and we can run our brand new command so, we'll type it:

node -v

What we're doing in this command is we're running the Node command, and we're passing in what's called a flag, a hyphen sign followed by a letter. It could be a, it could be j, or in our case it's v. This command will print the version of Node currently installed.

We might get an error like this:

If you try to run a command that doesn't exist, such as nodeasdf, you'll see command not found. If you see this, it usually means the Node installer didn't work correctly, or you haven't run it in the first place.

In our case though, running Node with the v flag should result in a number. In our case, it's version 9.3.0. If you do have Node installed, and you see something like the followingscreenshot, then you are done. In the next section, we'll start exploring exactly what Node is.

What is Node?

Node came about when the original developers took JavaScript, something you could usually only run inside the browser, and they let it run on your machine as a standalone process. This means that we could create applications using JavaScript outside the context of the browser.

Now, JavaScript previously had a limited feature set. When I used it in the browser, I could do things such as update the URL and remove the Node logo, adding click events or anything else, but I couldn't really do much more.

With Node, we now have a feature set that looks much more similar to other languages, such as Java, Python, or PHP. Some of these are as follows:

We can write Node applications using the JavaScript syntax

You can manipulate your filesystem, creating and removing folders

You can create query databases directly

You can even create web servers using Node

These were things that were not possible in the past, and they are because of Node.

Now, both Node and the JavaScript that gets executed inside of your browser, they're both running on the exact same engine. It's called the V8 JavaScript runtime engine. It's an open source engine that takes JavaScript code and compiles it into much faster machine code. And that's a big part of what makes Node.js so fast.

Machine code is low-level code that your computer can run directly without needing to interpret it. Your machine only knows how to run certain types of code, for example, your machine can't run JavaScript code or PHP code directly without first converting it into low-level code.

Using this V8 engine, we can take our JavaScript code, compile it to much quicker machine code, and execute that. This is where all those new features come in. The V8 engine is written in a language called C++. So if you want to extend the Node language, you don't write Node code, you write C++ code that builds off of what V8 already has in place.

Now, we'll not be writing any C++ code in this book. This book is not about adding onto Node, it is about using Node. So, we will only be writing JavaScript code.

Speaking of JavaScript code, let's start writing some inside Terminal. Now, throughout the book, we'll be creating files and executing those files, but we can actually create a brand new Node process by running the node command.

Referring to the following screenshot, I have a little right caret, which is waiting for JavaScript Node code, not a new command-prompt command:

This means that I can run something like console.log, which, as you probably already know, logs a message to the screen. log is a function, so I'll call it as such, opening and closing my parentheses, and passing in a string inside two single quotes, a message Hello world!, as shown in the following command line:

console.log('Hello world!');

This will print Hello world to the screen. If I hit enter, Hello world! prints just like you'd expect, as shown in the following code output:

Now, what actually happened behind the scenes? Well, this is what Node does. It takes your JavaScript code, it compiles it into machine code, and executes it. In the preceding code, you can see it executed our code, printing out Hello world!. Now, the V8 engine is running behind the scenes when we execute this command, and it's also running inside the Chrome browser.

If I open up the developer tools in Chrome by going to Settings | More Tools | Developer Tools:

I can ignore most of the things. I'm just looking for the Console tab, as shown in the following screenshot:

The preceding screenshot showing the console is a place where we can run some JavaScript code. I can type the exact same command, console.log('Hello world!'); and run it:

As you can see in the preceding screenshot, Hello world! prints to the screen, which is the exact same result we got when we ran it up earlier using Terminal. In both cases, we're running it through the V8 engine, and in both cases the output is the same.

Now, we already know that the two are different. Node has features such as filesystem manipulation, and the browser has features such as manipulating what's shown inside the window. Let's take a quick moment to explore their differences.

Differences between JavaScript coding using Node and in the browser

Inside the browser, you've probably used window if you've done any JavaScript development:

Window is the global object, it stores basically everything you have access to. In the following screenshot, you can see things such as array, we have all sorts of CSS manipulation and Google Analytics keywords; essentially every variable you create lives insideWindow:

We have something similar inside Node called global, as shown here:

It's not called window because there is no browser window in Node, thus it is called global. The global object stores a lot of the same things as window. In the following screenshot, you can see methods that might be familiar, such as setTimeout and setInterval:

If we look at this code screenshot, we have most of the things that are defined inside the window, with some exceptions, as shown in the following screenshot:

Now, inside the Chrome browser, I also have access to document:

The document object stores a reference to the Document Object Model (DOM) in the Node website. The document object shows exactly what I have inside the browser's viewport, as shown in the following screenshot:

I can make changes to the document to update what gets shown up on the browser's viewport. Now, obviously we don't have this HTML document inside Node, but we do have something similar, which is called process. You can view it by running process from Node, and in the following screenshot, we have a lot of information about the specific Node process that's being executed:

There's also methods available here to shut down the current Node process. What I'd like you to do is run the process.exit command, passing in as an argument the number zero, to say that things exited without error:

process.exit(0);

When I run this command, you can see I'm now back at the command prompt, as shown in the following screenshot:

I've left Node, and I'm at a place where I can run any regular command prompt command, such as checking my Node version. I can always get back into Node by running node, and I can leave it without using the process.exit command by using control+ C twice.

Now, I'm back at my regular command prompt. So, these are the notable differences, obviously inside the browser you have the viewable area, window gets changed to global, and a document basically becomes process. Now, obviously that's a generalization, but those are some of the big picture changes. We'll be exploring all the minutiae throughout the book.

Now, when someone asks you what is Node? You can say Node's a JavaScript runtime that uses the V8 engine. When they ask you what the V8 engine is, you can say the V8 engine is an open source JavaScript engine written in C++ that takes JavaScript code and compiles it to machine code. It's used inside Node.js and it's used in the Chrome browser.

Why use Node

In this section, we'll cover the why behind Node.js. Why is it so good at creating backend apps? And why is it becoming so popular with companies such as Netflix, Uber and Walmart, who are all using Node.js in production?

As you might have noticed since you're taking this course, when people want to learn a new backend language, more and more they're turning to Node as the language they want to learn. The Node skillset is in hot demand, for both frontend developers who need to use Node day to day to do things such as compile their applications, to engineers who are creating applications and utilities using Node.js. All of this has made Node the backend language of choice.

Now, if we look at the homepage of Node, we have three sentences, as shown in the following screenshot:

In the previous section, we addressed the first sentence. We took a look at what Node.js is. There's only three sentences in the image, so in this section, we'll take a look at the second two sentences. We'll read them now, then we'll break it down, learning exactly why Node is so great.

The first sentence, Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient; we'll explore all of this now. The second sentence we'll explore at the end of the section—Node.js' packaged ecosystem, npm, is the largest ecosystem of open source libraries in the world. Now, these two sentences have a ton of information packed into them.

We'll go over a few code examples, we'll dive into some charts and graphs, and we'll explore what makes Node different and what makes it so great.

Node is an event-driven, non-blocking language. Now, what is I/O? I/O is something that your application does all of the time. When you're reading or writing to a database, that is I/O, which is short form for input/output.

This is the communication from your Node application to other things inside of the Internet of Things. This could be a database read and write request, you may be changing some files on your filesystem, or you may be making an HTTP request to a separate web server, such as a Google API for fetching a map for the user's current location. All of these use I/O, and I/O takes time.

Now, the non-blocking I/O is great. That means while one user is requesting a URL from Google, other users can be requesting a database file read and write access, they can be requesting all sorts of things without preventing anyone else from getting some work done.

Blocking and non-blocking software development

Let's go ahead and take a look at the differences between blocking and non blocking software development:

In the preceding screenshot, I have two files that we'll be executing. But before going to that, first let's explore how each of these files operates, the steps that are required in order to finish the program.

This will help us understand the big differences between blocking, which I have on the left side of the image, which is not what Node uses, and non-blocking is on the right side, which is exactly how all of our Node applications in the book are going to operate.

You don't have to understand the individual details, such as what require is, in order to understand what's going on in this code example. We'll be breaking things down in a very general sense. The first line on each code is responsible for fetching a function that gets called. This function will be our simulated I/O function that is going to a database, fetching some user data and printing it to the screen.

Refer to the preceding code image. After we load in the function, both files try to fetch a user with an ID of 123. When it gets that user, it prints it to the screen with the user1 string first, and then it goes on and it fetches the user with 321 as the ID. And it prints that to the screen. And finally both files add up 1 + 2, storing the result, which is 3, in the sum variable and print it to the screen.

Now, while they all do the same thing, they do it in very different ways. Let's break down the individual steps. In the following code image, we'll go over what Node executes and how long it takes:

You can consider the seconds shown in the preceding screenshot; it doesn't really matter, it's just to show the relative operating speed between the two files.

The working non-blocking I/O

In our non-blocking example, this is how we'll be building our Node applications.

Let's break this code example down line by line. First up, things start much the same way as we discussed in the blocking example. We'll start the getUser function for user1, which is exactly what we did earlier:

But we're not waiting, we're simply kicking off that event. This is all part of the event loop inside Node.js, which is something we'll be exploring in detail.

Notice it takes a little bit of time; we're just starting the request, we're not waiting for that data. The next thing we do might surprise you. We're not printing user1 to the screen because we're still waiting for that request to come back, instead we start the process of fetching our user2 with the ID of 321:

In this part of the code, we're kicking off another event, which takes just a little bit of time to do-it is not an I/O operation. Now, behind the scenes, the fetching of the database is I/O, but starting the event, calling this function is not, so it happens really quickly.

Next up, we print the sum. The sum doesn't care about either of the two user objects. They're basically unrelated, so there's no need to wait for the users to come back before I print that sum variable, as shown in the following screenshot:

What happens after we print the sum? Well, we have the dotted box, as shown in the following screenshot:

This box signifies the simulated time it takes for our event to get responded to. Now, this box is the exact same width as the box in the first part of the blocking example (waiting on user1), as shown here:

Using non-blocking doesn't make our I/O operations any faster, but what it does do is it lets us run more than one operation at the same time.

In the non-blocking example, we start two I/O operations before the half second mark, and in between three and a half seconds, both come back, as shown in the following screenshot:

Now, the result here is that the entire application finishes much quicker. If you compare the time taken in executing both the files, the non-blocking version finishes in just over three seconds, while the blocking version takes just over six seconds. A difference of 50%. This 50% comes from the fact that in blocking, we have two requests each taking three seconds, and in non-blocking, we have two requests each taking three seconds, but they run at the same time.

Using the non-blocking model, we can still do stuff like printing the sum without having to wait for our database to respond. Now, this is the big difference between the two; blocking, everything happens in order, and in non-blocking we start events, attaching callbacks, and these callbacks get fired later. We're still printing out user1 and user2, we're just doing it when the data comes back, because the data doesn't come back right away.

Inside Node.js, the event loop attaches a listener for the event to finish, in this case for that database to respond back. When it does, it calls the callback you pass in the non-blocking case, and then we print it to the screen.

Now, imagine this was a web server instead of the preceding example. That would mean if a web server comes in looking to query the database, we can't process other users' requests without spinning up a separate thread. Now, Node.js is single threaded, which means your application runs on one single thread, but since we have non-blocking I/O, that's not a problem.

In a blocking context, we could handle two requests on two separate threads, but that doesn't really scale well, because for each request we have to beef up the amount of CPU and RAM resources that we're using for the application, and this sucks because those threads, are still sitting idle. Just because we can spin up other threads doesn't mean we should, we're wasting resources that are doing nothing.

In the non-blocking case, instead of wasting resources by creating multiple threads, we're doing everything on one thread. When a request comes in, the I/O is non-blocking so we're not taking up any more resources than we would be if it never happened at all.

Blocking and non-blocking examples using Terminal

Let's run these examples in real time and see what we get. And we have the two files (blocking and non-blocking files) that we saw in the previous section.

We'll run both of these files, and I'm using the Atom editor to edit my text files. These are things we'll be setting up later in the section, this is just for your viewing purpose, you don't need to run these files.

Now, the blocking and non-blocking files, will both get run and they'll do similar things to those we did in the previous section, just in a different way. Both use I/O operations, getUserSync and getUser, that take five seconds apiece. The time is no different, it's just the order they execute in that makes the non-blocking version much quicker.

Now, to simulate and show how things work, I'll add a few console.log statements as shown in the following code example, console.log('starting user1'), console.log('starting user2').

This will let us visualize how things work inside Terminal. By running node blocking.js, this is how we run files. We type node and we specify the filename, as shown in the following code:

node blocking.js

When I run the file, we get some output.starting user1prints to the screen and then it sits there:

Now, we have the user1 object printing to the screen with the name Andrew, and starting user2 prints to the screen, as shown in the following code output:

After that, the user2 object comes back around five seconds later with the name of Jen.

As shown in the preceding screenshot, our two users have printed to the screen, and at the very end our sum, which is 3, prints to the screen; everything works great.

Notice that starting user1 was immediately followed by the finishing of user1, and starting user2 was immediately followed by the finishing of user2 because this is a blocking application.

Now, we'll run the non-blocking file, which I've called non-blocking.js. When I run this file, starting user1 prints, starting user2 prints, then the sum prints all back to back:

Around 5 seconds later, at basically the same time, user1 and user2 both print to the screen.

This is how non-blocking works. Just because we started an I/O operation doesn't mean we can't do other things, such as starting another one and printing some data to the screen, in this case just a number. This is the big difference, and this is what makes non-blocking apps so fantastic. They can do so many things at the exact same time without having to worry about the confusion of multi-threading applications.

Let's move back into the browser and take a look at those sentences again in the Node website:

Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, and we saw that in action.

Because Node is non-blocking, we were able to cut down the time our application took by half. This non-blocking I/O makes our apps super quick, this is where the lightweight and efficient comes into play.

Node community – problem solving open source libraries

Now, let's go to the last sentence on the Node website, as shown in the following screenshot:

Node.js' package ecosystem, npm, is the largest ecosystem of open-source libraries in the world. This is what really makes Node fantastic. This is the cherry on top-the community, the people every day developing new libraries that solve common problems in your Node.js applications.

Things such as validating objects, creating servers, and serving up content live using sockets. There's libraries already built for all of those so you don't have to worry about this. This means that you can focus on the specific things related to your application without having to create all this infrastructure before you can even write real code, code that does something specific to your apps use case.

Now, npm, which is available on npmjs.org, is the site we'll be turning to for a lot of third-party modules:

If you're trying to solve a problem in Node that sounds generic, chances are that someone's already solved it. For example, if I want to validate some objects, let's say I want to validate that a name property exists and that there's an ID with a length of three. I could go into Google or go into npm; I usually choose Google, and I could Google search npm validate object.

When I google that, I'll just look for results from npmjs.com, and you can find the first three or so are from that:

I can click the first one, and this will let me explore the documentation and see if it's right for me:

This one looks great, so I can add it to my app without any effort.

Now, we'll go through this process. Don't worry, I'm not going to leave you high and dry on how to add third-party modules. We'll be using a ton of them in the book because this is what real Node developers do. They take advantage of the fantastic community of developers, and that's the last thing that makes Node so great.

This is why Node has come to the position of power that it currently sits at, because it's non-blocking, meaning it's great for I/O applications, and it has a fantastic community of developers. So, if you ever want to get anything done, there's a chance someone already wrote the code to do it.

This is not to say you should never use Rails or Python or any other blocking language again, that is not what I'm getting at. What I'm really trying to show you is the power of Node.js and how you can make your applications even better. Languages like Python have things such as the library Twisted, which aims to add non-blocking features to Python. Though the big problem is all of the third-party libraries, as they are still written in a blocking fashion, so you're really limited as to which libraries you can use.

Since Node was built non-blocking from the ground up, every single library on npmjs.com is non-blocking. So you don't have to worry about finding one that's non blocking versus blocking; you can install a module knowing it was built from the ground up using a non blocking ideology.

In the next couple of sections, you'll be writing your very first app and running it from Terminal.

Different text editors for node applications

In this section, I want to give you a tour of the various text editors you can use for this book. If you already have one you love using, you can keep using the one you have. There's no need to switch editors to get anything done in this book.

Now, if you don't have one and you're looking for a few options, I always recommend using Atom, which you can find at atom.io. It's free, open source, and it's available on all operating systems, Linux, macOS, and Windows. It's created by the folks behind GitHub and it's the editor that I'll be using inside of this book. There's an awesome community of theme and plug-in developers so you really can customize it to your liking.

Now, aside from Atom there are a few other options. I've heard a lot of people talking about Visual Studio Code. It is also open source, free, and available on all operating systems. If you don't like Atom, I highly recommend you check this out, because I've heard so many good things by word of mouth.

Next up, we always have Sublime Text, which you can find at sublimetext.com. Now, Sublime Text is not free and it's not open source, but it's a text editor that a lot of folks do enjoy using. I prefer Atom because it's very similar to Sublime Text, though I find it snappier and easier to use, plus it's free and open source.

Now, if you are looking for a more premium editor with all of the bells and whistles in IDE as opposed to a text editor, I always recommend JetBrains. None of their products are free, though they do come with a 30-day free trial, but they really are the best tools of the trade. If you find yourself in a corporate setting or you're at a job where the company is willing to pay for an editor, I always recommend that you go with JetBrains. All of their editors come with all of the tools you'd expect, such as version control integration, debugging tools, and deploying tools built in.

So, take a moment, download the one you want to use, play around with it, make sure it fits your needs, and if not, try another one.

Hello World – creating and running the first Node app

In this section, you will be creating and running your very first Node app. Well, it will be a simple one. It'll demonstrate the entire process, from creating files to running them from Terminal.

Creating the Node application

The first step will be to create a folder. Every project we create will go live inside of its own folder. I'll open up the Finder on macOS and navigate to my desktop. What I'd like you to do is open up the desktop on your OS, whether you're on Linux, Windows, or macOS, and create a brand new folder called hello-world.

I don't recommend using spaces in your project file or folder names, as it only makes it more confusing to navigate inside of Terminal. Now, we have this hello-world folder and we can open it up inside of our editor.

Now I'll use command + O (Ctrl + O for Windows users) to open up, and I'll navigate to the desktop and double-click my hello-world folder, as shown here:

On the left I have my files, which are none. So, let's create a new one. I'll make a new file in the root of the project, and we'll call this one app.js, as shown here:

This will be the only file we have inside our Node application, and in this file we can write some code that will get executed when we start the app.

In the future, we'll be doing crazy stuff like initializing databases and starting web servers, but for now we'll simply use console.log, which means we're accessing the log property on the console object. It's a function, so we can call it with parentheses, and we'll pass in one argument as string, Hello world!. I'll toss a semicolon on the end and save the file, as shown in the following code:

console.log('Hello world!');

This will be the first app we run.

Now, remember, there is a basic JavaScript requirement for this course, so nothing here should look too foreign to you. I'll be covering everything new and fresh inside of this course, but the basics, creating variables, calling functions, those should be something you're already familiar with.

Running the Node application

Now that we have our app.js file, the only thing left to do is to run it, and we'll do that over in Terminal. Now, to run this program, we have to navigate into our project folder. If you're not familiar with Terminal, I'll give you a quick refresher.

You can always figure out where you are using pwd on Linux or macOS, or the dir command on Windows. When you run it, you'll see something similar to the following screenshot:

I'm in the Users