Understanding Promise.allSettled() in JavaScript: A Comprehensive Guide

JavaScript provides a powerful toolkit for handling asynchronous operations, and one of the key players in this toolkit is the Promise object. While Promise.all() is widely known for handling multiple promises, its lesser-known sibling, Promise.allSettled(), can be just as valuable depending on the situation. In this blog, we will explore what Promise.allSettled() is, how it works, and when you should use it over other promise-handling methods.

1. Introduction to Promises in JavaScript

Before diving into Promise.allSettled(), it's essential to recall what promises are in JavaScript. A Promise represents the eventual completion (or failure) of an asynchronous operation and its resulting value.

A promise can be in one of these states:

• Pending: The initial state, neither fulfilled nor rejected.
• Fulfilled: The operation completed successfully.
• Rejected: The operation failed.

The Promise.all() method is frequently used to handle multiple promises in parallel, but it rejects if any one promise in the array is rejected. That's where Promise.allSettled() shines—it handles both fulfilled and rejected promises without halting the process.