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

Error handling in web workers

All the code in this chapter has made a naive assumption that the code running in our workers was error-free. Obviously, our workers will encounter situations where exceptions are thrown, or we'll just write buggy code during development—it's the reality we face as programmers. However, without proper error event handlers in place, web workers can be difficult to debug. Another approach we can take is to explicitly send back a message that identifies itself as being in an error state. We'll cover these two error-handling topics in this section.

Error condition checking

Let's say our main application code sends a message to a worker thread and expects to get some data in return. What if something goes wrong and the code that was expecting data needs to know about it? One possibility is to still send the message that the main thread is expecting; only that it has a field that indicates the errant state of the operation. The following illustration gives us an idea...