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

Chapter 4. Lazy Evaluation with Generators

Lazy evaluation is a programming technique, which is used when we don't want to compute values until the very last second. This way, we're sure we actually need it. The opposite approach, eager evaluation, has the potential to compute several values that aren't needed. This generally isn't a problem, until the size and complexity of our applications grow beyond a level where these wasted computations are imperceptible to the user.

The Generator is a new primitive type introduced to JavaScript as a part of the ES6 specification of the language. Generators help us implement lazy evaluation techniques in our code, and as a corollary, help us implement the conserve concurrency principle.

We'll start the chapter off with some simple introductions to generators, so we can get a feel for how they behave. From there, we'll move onto more advanced lazy evaluation scenarios, wrapping up the chapter with a look at coroutines. Let's get started.