Mastering the Promise Constructor: A Guide to Building Custom Async Operations in JavaScript

Learn how to create and manipulate promises from scratch using the Promise constructor

Photo by Rodion Kutsaiev on Unsplash

In the world of asynchronous JavaScript programming, promises have emerged as a powerful tool for managing and coordinating complex operations. While working with pre-existing promise-based APIs is a common practice, there are times when you need to create your own custom promises to encapsulate specific async behaviors.

Enter the Promise constructor, a built-in feature that allows you to create promises from scratch, tailoring them to your unique requirements.

The Promise constructor takes a single argument: an executor function. This executor function is responsible for initiating the asynchronous operation and resolving or rejecting the promise based on its outcome. It receives two callback functions, traditionally named resolve and reject, which you'll use to communicate the promise's eventual state.

Here’s a basic example of creating a promise using the constructor:

const myPromise = new Promise((resolve, reject) => {
  // Asynchronous operation goes here
  setTimeout(() => {
    const randomNumber = Math.random();
    if (randomNumber >=…