<h2>Introduction to the course</h2>Node.js is an event-driven runtime environment. By using JavaScript on the server and inheriting a rich library of modules it creates scalable, fast network applications.<h2>Who is this course for?</h2>Statistically, developers are more prone to side with JavaScript as their preferred programming language as JS is considered the most powerful, and therefore, Node.js has the highest technological ranking as well.If you&#x27;re looking to work with an environment that provides a wide range of uses for JavaScript development then you should try Node.js out.

Node.js

<h2>What does this lesson cover?</h2>Node.js tackles the standard, yet not always simple steps that bring a web server to its final form. This lesson focuses on the very specific nature of Node and defines the underlying meaning behind its infamous Event Drivent architecture and Asynchronous programming. Node has an edge when it comes to web development and it&#x27;s about time you discover it.

Introduction

<h2>What does this lesson cover?</h2>Node.js offers The Console Module which is a debugging-oriented console. The Console Module provides various methods to debug and construct streams on Node.js, and that will be the topic of this lesson.We&#x27;ll be thoroughly assessing each of the three main methods and with the help of code examples from standard Node.js applications and purpose-built quizzes, we&#x27;ll tackle the topic in no time.

Node.js Console

<h2>What does this lesson cover?</h2>In this lesson, we&#x27;ll be introducing Events as one of the core concepts in Node.js.The development of a new connection, the reading of a file, and every other move a computer takes are called an Event.The importance of Events stems from its full, in-depth definition and is clearly depicted in code examples from standard Node.js code.The Events Module of Node.js is the focus of the lesson and follows throughout the section as well.We&#x27;ll be dealing with the EventEmitter Object and Event handlers which will lead us to uncover the essence of Event-Driven Programming.

<h2>What does this lesson cover?</h2>Here we&#x27;ll be getting used to the Node.js environment, to do so of course, we&#x27;ll need to install it first.This lesson offers a step-by-step guide to installing the Node.js Environment and npm.

Installing Node.js

<h2>What does this lesson cover?</h2>We&#x27;ll be covering a mixture of both surface-level and key features of Node.js in this lesson.We&#x27;ll be going more in-depth into the prerequisites, including JavaScript knowledge, and distinguishments between Node.js and the browser.

Basic Concepts

<h2>What does this lesson cover?</h2>The introduction of the Node.js Module entails knowledge in loading built-in modules, listing and defining core modules, third-party modules (i.e. Express, and Mongoose), and local modules.This lesson aims at covering all the different topics listed while answering the question: &quot;Why use Node.js modules at all?&quot;.

Node.js Module Introduction

<h2>What does this lesson cover?</h2>Node&#x27;s ability to allow other tasks to proceed immediately instead of having to wait for the completion of certain prior tasks is reliant on the Event Loop.This lesson will explain the Event Loop and the exact steps that entail how it works. We&#x27;ll also compare and contrast Events and Callbacks, expand on the concept of Event Loop Ticks, Event Loop Blocking, and Escaping the Event Loop.

Event Loop

<h2>What does this lesson cover?</h2>After installing Node and the npm, it&#x27;ll be high time for you to run your first Node.js program.In this thorough lesson, we&#x27;ll be taking our first steps with the Command Line Interface (REPL terminal) and learning how to accept arguments from the command line.

Running Node.js

<h2>What does this lesson cover?</h2>Node.js objects emit a lot of events. We&#x27;ll be decribing the process of event emitting by incorporating callback function and inheritance.Additionally, the lesson covers the EventEmitter class of the events module entails methods that developers will be using quite often when coding Node.js applications. The methods we&#x27;ll refer to specifically are addListener(), removeListener(), removeAllListeners(), listeners(), once(), and emit().

Event Emitter

<h2>What does this lesson cover?</h2>The http module is made to support the wide range of Node.js features, hence the usage of the module proves valid for all developers working with Node.js.We&#x27;ll be addressing the module&#x27;s key properties with supporting code examples to enforce practice into our learning,

HTTP Module

Lesson Challenge

<h2>What does this lesson cover?</h2>URL parsings and resolution is executed with the help of the URL Module.This lesson covers implementations of URL properties with the usage of the URL module, we&#x27;ll also be using a lot of new methods (url.format(), url,resolve(), url.href, etc.), and expanding on terms like &quot;parsing&quot; and &quot;resolution&quot;.

URL Module

<h2>What does this lesson cover?</h2>The concept of Global Objects is widely popular in programming languages in general, they indicate the core objects that do not require installments.In the case of Node.js, Global Objects are a part of JavaScript and can be accessed without additional installments.This lesson covers the most-used Global Objects Node.js has to offer along with examples and lesson quizzes.

Globals

<h2>What does this lesson cover?</h2>The Node.js library has a wide range of utility modules available that have access to distinct utility functions.They are the OS Module, the Path Module, the Net Module, the DNS Module, and the Domain Module. This lesson will uncover the usage and structure of the said modules along with the reasoning behind their individual usage in Node.js applications.

Utility Modules

<h2>What does this lesson cover?</h2>We&#x27;ll be diving into the main characteristics of Node.js: Processes (The Process Object).This lesson will expand on defining the Process object with a thorough definition and initiation in code.Furthermore, we&#x27;ll get into the specifics of Processes such as Process Properties, Process Functions/Methods, Child Processes and how to create them, The Spawn Method, etc.

Processes

<h2>What does this lesson cover?</h2>The Callback function is the secret behind Node&#x27;s scalable and non-blocking architecture.This lesson will go into depth on the function and all its supporting methods including their benefits and how they work into all Node.js applications, ensuring their non-blocking nature in a couple of steps.

Callbacks

Event Emitter: Introduction

In Node a lot of objects emit events. For example, a file stream emits &quot;data&quot; whenever new data chunks have been read or a TCP server emits &quot;connect&quot; whenever a new client connects. Those objects in Node.js are called Event Emitters.

In simpler terms, Event Emitters permit developers to subscribe to the events they want to work with. To do so, developers attach callback functions (we’ve elaborated on these before) that will be declared whenever an event in said event emitter is initiated.

Node gives you the opportunity to either Inherit an Event Emitter or Create one. The latter will be referred to in further lessons. However, if you want to use Node’s Event Emitter, follow the code snippet below.

For importing the <samp>EventEmitter</samp> with all of its methods in (in this example) <samp>classConstructor</samp> instances, <samp>util.inherits</samp> needs to be set up as demonstrated.

Write Missing

Inherite an Event Emitter from <samp>util</samp>.

Event Emitter: Details

When you need access to constantly refreshed information, for example, notification every time data is available, callbacks won’t be able to handle that as efficiently as Event Emitter. The standard interface separates an emitter (a single event emitter) and event listeners (more than one, depending on the complexity of your program).

We’ve already defined event emitters, as for event listeners - they are attached to the event emitter and listen to ongoing requests.

In the above-displayed code snippet, you can trace the steps required to make an HTTP request to an HTTP server with Node’s http.request API. The http.request method initiates the callback that emits the data and end events. The result here is a newly registered callback function that will be initiated any time the data and end events take place.

Methods

In the events module, developers get the most use out of the <samp>EventEmitter</samp> class. Accessing it demands the <samp>require() </samp>method as such:

Some of the most used methods are described below, for the full list, access Node&#x27;s documentation.

‣addListener() the method adds a listener to the listener array, it is one of the most used methods and we&#x27;ll use it in the next lesson. It takes two arguments event and listener.‣removeListener() in simple terms, removes a listener from the array of listeners, but, will only remove a single instance. Pay attention to exactly how many times said listener that needs removing has been added to an array, and use the method that many times.‣removeAllListeners() is yet another method you should be careful with, removing all listeners in an event will consequently remove them if they&#x27;re present elsewhere in the code.‣listeners() simply returns an array of listeners‣once() adds a listener to an event for one-time use. Meaning, after the event is triggered, the listener will be utilized, and thus, removed completely.‣emit() takes on as many arguments as there are listeners that you want to execute (in the exact order you input them).

Select Correct Answer  

What does the <samp>.once()</samp> method achieve once declared?

Class Methods & Events

The method that the <samp>EventEmitter</samp> class takes on is the<samp> listenerCount</samp> event. It takes on two arguments, emitter and event. The method provides the number of listeners for a specified event, meaning it returns an integer and takes on a string type for the parameter. Find its clear syntax below:

There are two events worth mentioning, they are: <samp>removeListener </samp>and <samp>newListener</samp>.

The<samp> removeListener</samp> event is triggered every time developers remove listeners. This entails the removal of listeners from a listener array located in the event.The <samp>newListener</samp> event is utilized whenever developers decide to add new listeners to an existing array. Said event is declared prior to adding a listener to its internal array of listeners.

Binding Event Listeners

Node.js permits the usage of an events listener/listeners to listen to the same connection. For the preface, go over the code snippet below.

In the code snippet above, after initially declaring <samp>events</samp> with the <samp>require()</samp> method along with the <samp>EventEmitter </samp>instance, we binded the listener with the connection by utilizing the <samp>addListener()</samp> method.

If we were to bind multiple listeners to the same connection, it would go something along the lines of:

After declaring the second listener (l<samp>istenerB</samp>) we first binded it to the same connection as our initial listener (<samp>listener</samp>), and thus, with the <samp>myListeners </samp>variable, we&#x27;ve required<samp> events</samp>, and the binding of the two listeners to the same connection.

Select Correct Answer

Removing Event Listeners

If you no longer want the information on a defined event or object, you can simply remove the event listener by providing an account on the event type and callback function as displayed in the code snippet below.

The removal of the reading listener is highlighted in the last section of code, after declaring EventEmitter and executing the listener function.

The event listener can be removed for a number of reasons, the main one being future evet interference, redundancy, etc.

The leading cause of naming event listeners is that it will be referred to at least twice when adding and when removing the binding of a listener.

For conducting the removal of all the event listeners for a specified event type from an event emitter, utilize the below-mentioned line of code:

Under the event parameter you can log in, for example, the process interruption signal/event names.

Initiate the removal of all Event Listeners.

<h2>What does this section cover?</h2>This section introduces newbies to the absolute fundamentals and basics of Node.js. After defining Node.js and its perks, we&#x27;ll identify Node characteristics such as Event Driven Programming and Architectural Overview.Another area we&#x27;ll uncover is concepts of Node that every developer should know, including npm (Node Package Manager), two-way data binding, and other key features/concepts in Node.js.

Get Started

<h2>What does this section cover?</h2>This section will guide you to installing and then running your first ever Node.js application.The super exciting process does in fact entail a bit of work with environment setup, npm installation, and other intricate things you should shift your attention towards. Luckily, we&#x27;ll show you where to look!

Setup

<h2>What does this section cover?</h2>The core of all Node.js applications consists of every single term, concept, module, and method you&#x27;ll find in this section.We&#x27;ll introduce you to the HTTP, Node.js, Utility, and URL modules, processes, the callback function, and the console.The topics we&#x27;ll be covering are essentials and each brings its own benefits to the Node.js table, hence we&#x27;ll be referring to each topic individually, with supporting code examples and lesson quizzes.

The Core

<h2>What does this lesson cover?</h2>The development of a new connection, the reading of a file, and every other move a computer takes are called an Event.This section serves as a thorough representation of Events in Node.js, the Event Module, and the EventEmitter global object with the most used properties it offers Node developers.The purpose of the Event Module (as we&#x27;ll cover in the section) is to support Node&#x27;s non-block and event-driven programming style. Naturally, we&#x27;ll refer to the concept of event-driven programming as a whole and why Node.js is considered event-driven.

Node.js

Achievements

Event Emitter: Details

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