Book Image

JavaScript from Beginner to Professional

By : Laurence Lars Svekis, Maaike van Putten, Codestars By Rob Percival
4 (5)
Book Image

JavaScript from Beginner to Professional

4 (5)
By: Laurence Lars Svekis, Maaike van Putten, Codestars By Rob Percival

Overview of this book

This book demonstrates the capabilities of JavaScript for web application development by combining theoretical learning with code exercises and fun projects that you can challenge yourself with. The guiding principle of the book is to show how straightforward JavaScript techniques can be used to make web apps ranging from dynamic websites to simple browser-based games. JavaScript from Beginner to Professional focuses on key programming concepts and Document Object Model manipulations that are used to solve common problems in professional web applications. These include data validation, manipulating the appearance of web pages, working with asynchronous and concurrent code. The book uses project-based learning to provide context for the theoretical components in a series of code examples that can be used as modules of an application, such as input validators, games, and simple animations. This will be supplemented with a brief crash course on HTML and CSS to illustrate how JavaScript components fit into a complete web application. As you learn the concepts, you can try them in your own editor or browser console to get a solid understanding of how they work and what they do. By the end of this JavaScript book, you will feel confident writing core JavaScript code and be equipped to progress to more advanced libraries, frameworks, and environments such as React, Angular, and Node.js.
Table of Contents (19 chapters)
16
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17
Index

Event loop

We would like to end this chapter by explaining how JavaScript handles asynchrony and concurrency under the hood. JavaScript is a single-threaded language. A thread in this context means a path of execution. If there is only a single path, this means that tasks will have to wait for one another and only one thing can happen at a time.

This single executor is the event loop. It's a process that executes the actual work. You may wonder about this, because you've just learned about concurrency and doing things asynchronously and at the same time. Well, even though JavaScript is single-threaded, it doesn't mean that it cannot outsource some tasks and wait for them to come back. This is exactly how JavaScript manages to do things in a multithreaded manner.

Call stack and callback queue

JavaScript works with a call stack, and all the actions that it has to execute are queued up here. The event loop is a process that is constantly monitoring this call...