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

Execution contexts

Now it's time to look at the JavaScript interpreter itself—the component that takes over from other browser components when events take place and code needs to run. There's always an active JavaScript context, and within the interpreter, we'll find a stack of contexts. This is similar to many programming languages where stacks control the active context.

Think of the active context as a snapshot of what's happening right now in our JavaScript code. A stack structure is used because the active context can change to something else, such as when a function is called. When this happens, a new snapshot is pushed onto the stack, becoming the active context. When it's done running, it's popped from the stack, leaving the next context as the active context.

In this section, we'll take a look at how the JavaScript interpreter handles context switching, and the internal job queue that manages the context stack.

Maintaining execution state

The stack of contexts within the JavaScript...