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

What are workers?

Before we dive into implementation examples, this section will give us a quick conceptual breakdown of what web workers are. It's good to know exactly how web workers cooperate with the rest of the system under the hood. Web workers are operating system threads—a target where we can dispatch events, and they execute our JavaScript code in a truly parallel fashion.

OS threads

At their core, web workers are nothing more than operating system-level threads. Threads are kind of like processes, except they require less overhead because they share memory addresses with the process from which they're created. Since the threads that power web workers are at the level of the operating system, we're at the mercy of the system and its process scheduler. Most of the time, this is exactly what we want—let the kernel figure out when our JavaScript code should run in order to best utilize the CPU.

Here's a diagram showing how the browser maps its web workers to OS threads, and how these...