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
PacktPub.com
Contributors
Preface
Index

An introduction to the concept of threads


Simply put, a thread is a simple and independent snippet of running code. It is a container in which your tasks get executed. Before web workers, JavaScript provided just a single thread; that is, the main thread for the developers to do everything in.

This created some problems with advancements in tech. Suppose you're running a smooth CSS3 animation, and suddenly you need to do a heavy calculation on the JavaScript end for some reason. This'll make the animation sluggish if you do it on the main thread. However, if you offload it to a web worker that runs in its own thread, it will have no effect on the user experience.

Because web workers run in their own threads, they cannot have access to the following:

  • DOM: It is not thread-safe to access it from web workers and the main UI script
  • parent object: Basically, this gives access to some DOM APIs that for the same reason as stated above, would be thread-unsafe to access
  • window object: BOM (Browser Object...