Book Image

JavaScript Concurrency

By : Adam Boduch
Book Image

JavaScript Concurrency

By: Adam Boduch

Overview of this book

Concurrent programming may sound abstract and complex, but it helps to deliver a better user experience. With single threaded JavaScript, applications lack dynamism. This means that when JavaScript code is running, nothing else can happen. The DOM can’t update, which means the UI freezes. In a world where users expect speed and responsiveness – in all senses of the word – this is something no developer can afford. Fortunately, JavaScript has evolved to adopt concurrent capabilities – one of the reasons why it is still at the forefront of modern web development. This book helps you dive into concurrent JavaScript, and demonstrates how to apply its core principles and key techniques and tools to a range of complex development challenges. Built around the three core principles of concurrency – parallelism, synchronization, and conservation – you’ll learn everything you need to unlock a more efficient and dynamic JavaScript, to lay the foundations of even better user experiences. Throughout the book you’ll learn how to put these principles into action by using a range of development approaches. Covering everything from JavaScript promises, web workers, generators and functional programming techniques, everything you learn will have a real impact on the performance of your applications. You’ll also learn how to move between client and server, for a more frictionless and fully realized approach to development. With further guidance on concurrent programming with Node.js, JavaScript Concurrency is committed to making you a better web developer. The best developers know that great design is about more than the UI – with concurrency, you can be confident every your project will be expertly designed to guarantee its dynamism and power.
Table of Contents (17 chapters)
JavaScript Concurrency
About the Author
About the Reviewer

Everything is a task

When we visit a web page, a whole environment is created for us within the browser. This environment has several subsystems that enable the webpage we're looking at to look and behave as it should according to World Wide Web Consortium (W3C) specs. Tasks are the fundamental abstraction inside a web browser. Anything that happens is either a task itself, or a smaller part of a larger task.


If you're reading any of the W3C specifications, the term "user agent" is used instead of "web browser". In 99.9% of cases, the major browser vendors are what we're reading about.

In this section, we'll look at the major components of these environments, and how task queues and event loops facilitate the communication between these components, to realize the overall appearance and behavior of the web page.

Meet the players

Let's introduce some terminology that will help us throughout the various sections in this chapter:

  • Execution environment: This container gets created whenever...