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

Keeping the DOM responsive

So far in this chapter, the focus has been data-centric—taking input and transforming it by using web workers to divide and conquer. This isn't the only use of worker threads; we can also use them to keep the DOM responsive for our users.

In this section, we'll introduce a concept that's used in Linux kernel development to split events into phases for optimal performance. Then, we'll address the challenge of communicating between the DOM and our workers and vice-versa.

Bottom halves

The Linux kernel has the concept of top-halves and bottom-halves. This idea is used by the hardware interrupt request machinery. The problem is that hardware interrupts happen all the time, and it's this kernel's job to make sure they're all captured and processed in a timely-manor. To do this effectively, the kernel splits the task of processing a hardware interrupt into two halves—the top and bottom half.

It's the job of the top-half to respond to external stimuli, such as a mouse click...