Promises in Javascript

luhan

This thread will be talking about promises and this is a continuation of the async functions post. Click on this link “https://afr.ng/8cf2385e” if you haven’t read the async/await post.

So JavaScript is all about keeping things moving, but sometimes you have got to wait for something to finish. Promises are here to ensure you don’t get stuck in code limbo!

What are Promises?

Promises are objects that represent the eventual completion (or failure) of an asynchronous operation. They act like a placeholder, saying “Hey, I’ll get you the result when it’s done.”

Think of it like an order: Imagine you order a pizza. You don’t get it right away, but the restaurant gives you a receipt (the promise) saying they’ll deliver it eventually. The receipt tells you it’ll be delicious (resolved promise) or burnt (rejected promise).

luhan

Key points about Promises:

States of a Promise: A promise can be in three states: pending (waiting), fulfilled (finished successfully), or rejected (failed).
Waiting with then: You can use the then method to specify what to do with the result (like eating your pizza) once the promise is fulfilled.
Handling Errors with catch: The catch method allows you to handle any errors (like a burnt pizza) that might occur during the asynchronous operation.

I prefer the try…catch where you wait for your line of code with async/await method more than traditional .then.

Interestingly, react also provides the Promise.all(), Promise.resolve(), and Promise.reject() method and this is why I enjoy writing code because there are always new/exciting things to learn

Simplythebest

I am yet to master the promise.all()

luhan

Simplythebestpromise.allalways returns a single promise. Either a fulfilled promise or a rejected one. It’s almost like promise.fulfill and promise.reject except that you give it more than one argument.

jenny

This is one of the areas that you must master as a javascript engineer especially when communicating with external APIs.