Object-Oriented JavaScript — Singletons and Decorators

Object-Oriented JavaScript — Singletons and Decorators

2 simple design patterns to follow.

JavaScript is partly an object-oriented language.

To learn JavaScript, we got to learn the object-oriented parts of JavaScript.

In this article, we’ll look at some basic design patterns.

Class-Like Singleton

We can create a singleton object by storing the class instance in a global object.

For instance, we can write:

function Foo() {
  if (typeof globalFoo === "undefined") {
    globalFoo = this;
  return globalFoo;

then we can create a Foo instance by writing:

const a = new Foo();
const b = new Foo();
console.log(a === b);

And the console log should log true since we store the existing instance in a global variable.

Then we returned it if it’s not undefined .

Singleton Stored in the Property of the Constructor

We know we shouldn’t use global variables, so we can store the singleton instance as a property of the constructor instead.

Functions can have properties since they are objects.

So we can write:

function Foo() {
  if (typeof Foo.instance === "undefined") {
    Foo.instance = this;
  return Foo.instance;

The only change is that we store the property in the instance instead of in a global variable.

We can also store it in a private property if we put it in a function.

So we can write:

const Foo = (() => {
  let instance;
  return function() {
    if (typeof instance === "undefined") {
      instance = this;
    return instance;

and do the same thing.

This way, we can’t accidentally change the instance to something else.

technology programming javascript

Bootstrap 5 Complete Course with Examples

Bootstrap 5 Tutorial - Bootstrap 5 Crash Course for Beginners

Nest.JS Tutorial for Beginners

Hello Vue 3: A First Look at Vue 3 and the Composition API

Building a simple Applications with Vue 3

Deno Crash Course: Explore Deno and Create a full REST API with Deno

How to Build a Real-time Chat App with Deno and WebSockets

Convert HTML to Markdown Online

HTML entity encoder decoder Online

JavaScript: Chessboard Program

Exercise from Eloquent JavaScript. Today, we will write a function that forms a chessboard. You can find the exercise in the Eloquent Javascript book (3rd edition, chapter 2; Program Structure). Write a program that creates a string that represents an 8×8 grid, using newline characters to separate lines. At each position of the grid there is either a space or a “#” character. The characters should form a chessboard.

Learning JavaScript: Development Environments for JavaScript Programming

One of the nice things about learning JavaScript these days is that there is a plethora of choices for writing and running JavaScript code. In this article, I’m going to describe a few of these environments and show you the environment I’ll be using in this series of articles.

Learning JavaScript: Data Types and Variables

To paraphrase the title of an old computer science textbook, “Algorithms + Data = Programs.” The first step in learning a programming language such as JavaScript is to learn what types of data the language can work with. The second step is to learn how to store that data in variables. In this article I’ll discuss the different types of data you can work with in a JavaScript program and how to create and use variables to store and manipulate that data.

[ Professor JavaScript ]: Introduction

Professor JavaScript is a JavaScript online learning courses YouTube Channel. Students can learn how to develop codes with JavaScript from basic to advanced levels through the online courses in this YouTube channel.

Introduction to JavaScript Async Programming

Async callbacks or promises. Introduction to JavaScript Async Programming