Book Image

ECMAScript Cookbook

By : Ross Harrison
Book Image

ECMAScript Cookbook

By: Ross Harrison

Overview of this book

ECMAScript Cookbook follows a modular approach with independent recipes covering different feature sets and specifications of ECMAScript to help you become an efficient programmer. This book starts off with organizing your JavaScript applications as well as delivering those applications to modem and legacy systems. You will get acquainted with features of ECMAScript 8 such as async, SharedArrayBuffers, and Atomic operations that enhance asynchronous and parallel operations. In addition to this, this book will introduce you to SharedArrayBuffers, which allow web workers to share data directly, and Atomic operations, which help coordinate behavior across the threads. You will also work with OOP and Collections, followed by new functions and methods on the built-in Object and Array types that make common operations more manageable and less error-prone. You will then see how to easily build more sophisticated and expressive program structures with classes and inheritance. In the end, we will cover Sets, Maps, and Symbols, which are the new types introduced in ECMAScript 6 to add new behaviors and allow you to create simple and powerful modules. By the end of the book, you will be able to produce more efficient, expressive, and simpler programs using the new features of ECMAScript. ?
Table of Contents (20 chapters)
Title Page
Copyright and Credits
Dedication
PacktPub.com
Contributors
Preface
Index

Awaiting multiple results concurrently


Sometimes it's possible to initiate multiple asynchronous operations at the same time. This can be desirable, for example, if multiple network requests are necessary in order to fetch all the data for a given page. Waiting for each request to finish before starting the next one wastes time.

In this recipe, we'll see how to use await to initiate and wait for multiple results concurrently.

Getting ready

This recipe assumes you already have a workspace that allows you to create and run ES modules in your browser. If you don't, please see the first two chapters.

How to do it...

  1. Open your command-line application and navigate to your workspace.
  2. Create a new folder named 04-05-await-concurrently.
  3. Create three functions, checkEngines, checkFlightPlan, andcheckNavigationSystem that log a message when they start and return a Promise that resolves to true if a random number is higher than a threshold after some timeout:
function checkEngines() { 
  console.log('checking...