JavaScript Promises: Promise.all vs Promise.allSettled vs Promise.race vs Promise.any

Ever wanted to be a “Promises whizz”. There are a few tricks you can learn to become that through the use of some promise static methods

On your way to become a “JavaScript Superstar” and “Promises whizz”, you’ll need to master the concept of handling multiple promises at the same time. There are some methods that are provided by the language to do just that, but before we dwell on those methods let’s begin with understanding some basics of “states” and “fates” of promises.

States and Fates

Promises generally have 3 possible mutually exclusive states, they are:

fulfilled — A promise is “fulfilled” if promise.then(f) will call f as soon as possible
rejected — A promise is rejected if promise.then(undefined, r) will call r “as soon as possible.”
pending — A promise is pending if it is neither “fulfilled” nor “rejected”.

An umbrella term, commonly used, for the above would be “settled” where a promise is said to be “settled” if it is not pending (that is if it is either fulfilled or rejected).

Promises have two possible mutually exclusive fates, they are:

resolved — A promise is “resolved” if trying to resolve or reject it has no effect, that is the promise has been locked-in to either follow another promise (“thenable” value) or has been “fulfilled” or “rejected”.
unresolved — A promise is “unresolved” if it is not resolved, that is if trying to resolve or reject it will have an impact on the promise.

Now that we have covered the concept of states and fates, we should now be able to understand promise concepts with common terminology. Let’s move on to the gist of the article.

#javascript #programming #developer

What is GEEK

Buddha Community

JavaScript Promises: Promise.all vs Promise.allSettled vs Promise.race vs Promise.any

Geeks Tutorial Point

1590928341

Promise.allSettled() vs Promise.all()

Promise.allSetlled() is recently introduced in ECMA 2020.
Check out how it is different from Promise.all()

https://www.geekstutorialpoint.com/2020/05/promiseallsettled-vs-promiseall.html

#javascript #promise.all #promise.allsettled #ecma #promise #jquery

Julie Donnelly

1602406920

JavaScript Promise: Methods Comparison

Introduction

Promises in JavaScript are used to handle asynchronous operations by keeping track of whether a certain event has happened. If that certain event has taken place, it determines what happens next. Promises return a value which is either a resolved value or a reason why it’s rejected. They can handle multiple asynchronous operations easily and they provide better error handling than callbacks and events.

Callback: A callback is a function that is passed into another function as an argument to be executed later.

Events: Events provide a dynamic interface to a WebPage and are connected to elements in the Document Object Model(DOM), for example: onclick(), onmouseover() etc.

A Promise has four states

Pending: Before the event has happened, the promise is in the pending state.

Settled: Once the event has happened it is then in the settled state.

Fulfilled: Action related to the promise has succeeded.

Rejected: Action related to the promise has failed.

#javascript #javascript-development #javascript-tutorial #promises #javascript-tips

Jacquelyn Marks

1591912500

All vs AllSettled vs Race

In this video, we are going to go over promises and three different promise methods that you can use when writing JavaScript or Node code.

#javascript #race #allsettled

Wilford Pagac

1607932910