The Promise.allSettled() static method takes an iterable of promises as input and returns a single Promise. This returned promise fulfills when all of the input's promises settle (including when an empty iterable is passed), with an array of objects that describe the outcome of each promise.
Syntax
Promise.allSettled(iterable)
Parameters
Return value
A Promise that is:
- Already fulfilled, if the
iterablepassed is empty. Asynchronously fulfilled, when all promises in the given
iterablehave settled (either fulfilled or rejected). The fulfillment value is an array of objects, each describing the outcome of one promise in theiterable, in the order of the promises passed, regardless of completion order. Each outcome object has the following properties:status- : A string, either
"fulfilled"or"rejected", indicating the eventual state of the promise.
- : A string, either
value- : Only present if
statusis"fulfilled". The value that the promise was fulfilled with.
- : Only present if
reason- : Only present if
statusis"rejected". The reason that the promise was rejected with.
- : Only present if
If the
iterablepassed is non-empty but contains no pending promises, the returned promise is still asynchronously (instead of synchronously) fulfilled.
Description
The Promise.allSettled() method is one of the promise concurrency methods. Promise.allSettled() is typically used when you have multiple asynchronous tasks that are not dependent on one another to complete successfully, or you'd always like to know the result of each promise.
In comparison, the Promise returned by Promise.all may be more appropriate if the tasks are dependent on each other, or if you'd like to immediately reject upon any of them rejecting.
Examples
Using Promise.allSettled()
Promise.allSettled([
Promise.resolve(33),
new Promise((resolve) => setTimeout(() => resolve(66), 0)),
99,
Promise.reject(new Error("an error")),
]).then((values) => console.log(values));
// [
// { status: 'fulfilled', value: 33 },
// { status: 'fulfilled', value: 66 },
// { status: 'fulfilled', value: 99 },
// { status: 'rejected', reason: Error: an error }
// ]