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

Synchronizing several promises

Until this point in the chapter, we've looked at single promise instances that resolve a value, trigger callbacks, and possibly cause other promises to resolve. In this section, we'll look at a couple of static Promise methods that help us in scenarios where we need to synchronize the resolution of several promise values.

First, we'll address the common case where a component that we develop requires synchronous access to several asynchronous resources. Then, we'll look at the less common scenario where asynchronous actions become irrelevant before they're resolved due to events that have taken place in the UI.

Waiting on promises

In the case where we are waiting for several promises to resolve, perhaps to transform multiple data sources into something consumable by a UI component, we can use the Promise.all() method. It takes a collection of promise instances as input, and returns a new promise instance. This new instance is resolved only when all of the input...