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Promise.allSettled() – What Is the JavaScript Promise allSettled() Method?

Promise.allSettled() is a static method of the Promise constructor function. It returns a new promise object after the fulfillment or rejection of all the items in the iterable value you’ve provided as its argument.

Syntax of the Promise.allSettled() Static Method

Promise.allSettled(iterable);
  • The allSettled() method’s iterable argument’s items can be promises, thenables, or any of JavaScript’s data types.
  • Promise.allSettled() will automatically pass each of its iterable argument’s items through Promise.resolve(). Therefore, allSettled() will eventually resolve all its iterable argument’s values to a fully-fledged promise object.

Example of Promise.allSettled() Returning a Fulfilled Promise

Promise.allSettled(["Orange", Promise.resolve(24), 715]);


// The invocation above will return:
Promise { <state>: "fulfilled", <value>: Array(3) [
  { status: "fulfilled", value: "Orange" },
  { status: "fulfilled", value: 24 },
  { status: "fulfilled", value: 715 }
]}

The snippet above returned a new promise object after JavaScript resolved all the method’s array items.

When Does Promise.allSettled() Return a Fulfilled Promise?

Promise.allSettled() returns a fulfilled promise when the static method resolves all the items in its iterable argument.

Here’s an example:

const item1 = Promise.resolve(24);
const item2 = 715;
const item3 = new Promise((resolve, reject) => {
  setTimeout(() => {
    resolve("Orange");
  }, 15000);
});


Promise.allSettled([item1, item2, item3]).then((value) => {
  console.log(value);
});


// The invocation above will first return:
// Promise { <state>: "pending" }


// Then, after 15000 milliseconds (15 seconds), the invocation will return:
Array(3) [
  { status: "fulfilled", value: 24 },
  { status: "fulfilled", value: 715 }
  { status: "fulfilled", value: "Orange" },
]

The snippet above returned a fulfilled promise after JavaScript resolved all the array argument’s items.

When Does Promise.allSettled() Return a Rejected Promise?

Promise.allSettled() returns a rejected promise when the static method resolves all the items in its iterable argument.

Here’s an example:

const item1 = Promise.reject(24);
const item2 = 715;
const item3 = Promise.reject("Pinkmelon");
const item4 = new Promise((resolve, reject) => {
  setTimeout(() => {
    resolve("Orange");
  }, 15000);
});


Promise.allSettled([item1, item2, item3, item4]).then((value) => {
  console.log(value);
});


// The invocation above will first return:
// Promise { <state>: "pending" }


// Then, after 15000 milliseconds (15 seconds), the invocation will return:
Array(4) [
  { status: "rejected", reason: 24 }
  { status: "fulfilled", value: 715 }
  { status: "rejected", reason: "Pinkmelon" },
  { status: "fulfilled", value: "Orange" },
]

The snippet above returned a rejected promise after JavaScript resolved all the array argument’s items.

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