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

Checking instance type with instanceOf


There are many situations, such as argument validation, where we'll want to check the class of an object. Because JavaScript is not statically typed, we can't guarantee that a function receives an argument of the correct type before the program starts, and we need to check at runtime.

In this recipe, we'll see how to use the instanceOf operator to check an object's prototype at runtime.

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 07-04-checking-with-instanceof.
  3. Copy or create an index.html that loads and runs a main function from main.js.
  1. Create a main.js with two identical classes, Rocket and InactiveRocket:
// main.js class Rocket { 
  constructor(name) { 
    this.name = name; 
  } 
} 
 
class InactiveRocket { 
  constructor...