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

Fixing one billion count with atomics


Now we know the reason for our garbage value, and, with atomics, it should be easy to fix the problem. Right? Wrong.

There is a massive performance penalty on using atomic locking a billion times. Let's look at our updated worker.js code now:

// worker.js
let sharedMem;

addEventListener('message', ({data}) => {
  //console.log(data);
    if(data.message == 'sab') {
        sharedMem = data.memory;
        console.log('Memory ready');
    }
    if(data.cmd == 'start') {
      console.log('Iterations ready');
        startCounting(data.iterations);
    }
});

function startCounting(limit) {
    const arr = new Uint32Array(sharedMem);
    for(let i=0;i<limit;i++) {
        Atomics.add(arr, 0, 1);
    }
    postMessage('done')
}

This is similar to our previous implementation of the problem, with the change being that instead of adding it directly to the array, we are performing an atomic operation so that the value isn't changed by the other thread while...