Book Image

Learn ECMAScript - Second Edition

By : MEHUL MOHAN, Narayan Prusty
Book Image

Learn ECMAScript - Second Edition

By: MEHUL MOHAN, Narayan Prusty

Overview of this book

Learn ECMAScript explores implementation of the latest ECMAScript features to add to your developer toolbox, helping you to progress to an advanced level. Learn to add 1 to a variable andsafely access shared memory data within multiple threads to avoid race conditions. You’ll start the book by building on your existing knowledge of JavaScript, covering performing arithmetic operations, using arrow functions and dealing with closures. Next, you will grasp the most commonly used ECMAScript skills such as reflection, proxies, and classes. Furthermore, you’ll learn modularizing the JS code base, implementing JS on the web and how the modern HTML5 + JS APIs provide power to developers on the web. Finally, you will learn the deeper parts of the language, which include making JavaScript multithreaded with dedicated and shared web workers, memory management, shared memory, and atomics. It doesn’t end here; this book is 100% compatible with ES.Next. By the end of this book, you'll have fully mastered all the features of ECMAScript!
Table of Contents (18 chapters)
Title Page

Introduction to web workers

The web worker is, essentially, a piece of JS code which does not run in the same thread as your main application. And by thread, I literally mean a different thread. The web workers truly enable JS to work in a multi-threaded mode. A question that might arise here is, What are the differences between asynchronous operations and web workers?

If you think about it, they are more or less the same thing. The web workers take away loads from the main thread for a while and then come back with the results. However understand the fact that async functions run on the UI thread, whereas web workers do not. Also, web workers are long-lived, and live inside a separate thread, whereas asynchronous operators, as we discussed in Chapter 4, Asynchronous Programming, follow the Event loop.

Performance-wise, web workers are also much faster than traditional asynchronous operations. Here's a test which sorts randomly generated arrays of lengths 10K and 1M as an asynchronous operation...