Promise.allSettled

By  on  

The Promise object has many useful functions like all, resolve, reject, and race -- stuff we use all the time. One function that many don't know about is Promise.allSettled, a function that fires when all promises in an array are settled, regardless of whether any of the promises are resolved or rejected.

Promise.all is great but then isn't called if a project is rejected:

Promise.all([
  Promise.resolve(1),
  Promise.resolve(true),
  Promise.reject("Boooooo"),
])
.then(_ => console.log("Then!"))
.catch(e => console.log("catch!"));

// Catch!

There are always going to be cases where you'd like to run the then function regardless of individual results -- think hiding a spinner image at the end of multiple fetch requests; that's where Promise.allSettled comes in:

Promise.allSettled([
  Promise.resolve(1),
  Promise.resolve(true),
  Promise.reject("Boooooo"),
])
.then(promiseResults => console.log("Then! ", promiseResults))
.catch(e => console.log("catch!"));

/*
Then!
[
  { status: "fulfilled", value: 1 },
  { status: "fulfilled", value: true },
  { status: "rejected", reason: "Boooooo" }
]
*/

Promise.allSettled is awesome -- certainly much better than an old shim floating around years ago. Between all, allSettled, and race, as well as the ability to cancel fetch requests, we've almost got every aspect of Promises covered!

Recent Features

  • By
    Designing for Simplicity

    Before we get started, it's worth me spending a brief moment introducing myself to you. My name is Mark (or @integralist if Twitter happens to be your communication tool of choice) and I currently work for BBC News in London England as a principal engineer/tech...

  • By
    5 Awesome New Mozilla Technologies You’ve Never Heard Of

    My trip to Mozilla Summit 2013 was incredible.  I've spent so much time focusing on my project that I had lost sight of all of the great work Mozillians were putting out.  MozSummit provided the perfect reminder of how brilliant my colleagues are and how much...

Incredible Demos

Discussion

  1. I think the rejected results in the last code block should be:

     status: 'rejected', reason: 'Boooooo' }
  2. My only problem with this approach is that the .catch block never gets called with Promise.allSettled()

    • Werner

      Yes, that is import! Thank you Michel! Please correct that David.

  3. Terry

    So with allSettled is the .catch handler deprecated? When is it hit? Same with the onRejected param to then?

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!