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Professional JavaScript

You're reading from Professional JavaScript Fast-track your web development career using the powerful features of advanced JavaScript

Product type Paperback

Published in Sep 2019

Publisher

ISBN-13 9781838820213

Length 664 pages

Edition 1st Edition

Languages

JavaScript

Tools

Cheerio

Concepts

Web Programming

Authors (4):

Hugo Di Francesco

Siyuan Gao

Vinicius Isola

Philip Kirkbride

View More author details

Table of Contents (12) Chapters

Preface

About the Book

1. JavaScript, HTML, and the DOM FREE CHAPTER

2. Node.js and npm

3. Node.js APIs and Web Scraping

4. RESTful APIs with Node.js

5. Modular JavaScript

6. Code Quality

7. Advanced JavaScript

8. Asynchronous Programming

9. Event-Driven Programming and Built-In Modules

10. Functional Programming with JavaScript

Appendix

9. Event-Driven Programming and Built-In Modules

Activity 13: Building an Event-Driven Module

Solution:

Perform the following steps to complete this activity:

Import the events module:
```
const EventEmitter = require('events');
```
Create the SmokeDetector class that extends EventEmitter and set batteryLevel to 10:
```
class SmokeDetector extends EventEmitter {
    constructor() {
        super();
        this.batteryLevel = 10;
    }
}
```
In our constructor, because we are extending the EventEmitter class and we are assigning a custom property, batteryLevel, we will need to call super inside the constructor and set batteryLevel to 10.
Create a test method inside the SmokeDetector class that will test the battery level and emit a low battery message in the event that the battery is low:
```
test() {
        if (this...
```

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Authors (4)

1 of 4

Hugo Di Francesco

Hugo Di Francesco

Hugo Di Francesco is a software engineer who has worked extensively with JavaScript. He holds a MEng degree in mathematical computation from University College London (UCL). He has used JavaScript across the stack to create scalable and performant platforms at companies such as Canon and Elsevier and in industries such as print on demand and mindfulness. He is currently tackling problems in the travel industry at Eurostar with Node.js, TypeScript, React, and Kubernetes while running the eponymous Code with Hugo website. Outside of work, he is an international fencer, in the pursuit of which he trains and competes across the globe.

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Siyuan Gao

Siyuan Gao

Siyuan Gao is a software engineer at Electronic Arts. He has a bachelor's degree in computer science from Purdue University. He has worked with JavaScript and Node.js for over 4 years, mainly building efficient backend solutions for high-availability systems. He is also a contributor to the Node.js Core project and has had many npm modules published. In his spare time, he enjoys learning about video game design and machine learning.

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Vinicius Isola

Vinicius Isola

Vinicius Isola started programming back in 1999 using Macromedia Flash and ActionScript. In 2005, he took the Java Certification and specialized in building web and enterprise applications. Always working on all parts of the stack, JavaScript and web technologies have always been present in his many job roles and the companies he has worked for. In his free time, he likes to work on open-source projects and mentor new developers.

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Philip Kirkbride

Philip Kirkbride

Philip Kirkbride has over 5 years of experience with JavaScript and is based in Montreal. He graduated from a technical college in 2011 and since then he has been working with web technologies in various roles.

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