JavaScript Promise allSettled() Method

Promise.allSettled() method in JavaScript is used to handle multiple promises concurrently and return a single promise. This promise is fulfilled with an array of promise state descriptors, each describing the outcome of the corresponding promise in the input array. Unlike Promise.all(), Promise.allSettled() does not short-circuit when one of the promises is rejected; instead, it waits for all promises to settle, providing information about each one.

Syntax:

Promise.allSettled(iterable);

Parameters:

This method accepts a single parameter iterable which takes an array of promises or a normal array that contains some objects.

Return Value:

This method returns the following values:

• If the passed argument is empty, it returns a Promise that is already resolved.
• For all other cases, it returns a pending Promise, along with the status as well as the values of all promises that are passed inside it individually.

Example 1: In this example, we will use the Promise allSettled() Method

Javascript

// Illustration of Promise.allSettled()
// Method in Javascript with Example

const p1 = Promise.resolve(50);
const p2 = new Promise((resolve, reject) =>
    setTimeout(reject, 100, 'geek'));
const prm = [p1, p2];

Promise.allSettled(prm).
    then((results) => results.forEach((result) =>
        console.log(result.status, result.value)));

Output

fulfilled 50
rejected undefined

Example 2: In this example, we will use the Promise allSettled() Method

Javascript

// Simple promise that resolves
// After a given time
const tOut = (t) => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            resolve(`Completed in ${t}`)
        }, t)
    })
}

// Resolving a normal promise
tOut(1000).then(result => console.log(result))
// Completed in 1000

// Promise.allSettled
Promise.allSettled([tOut(1000), tOut(2000)]).then(result =>
    console.log(result))

Output:

"Completed in 1000"
Array [Object { status: "fulfilled", value: "Completed in 1000" }, 
Object { status: "fulfilled", value: "Completed in 2000" }]

Example 3: In this example, we have displayed the exact output which is received whenever we execute multiple promises and pass them inside Promise.allSettled() method.

Javascript

let first_promise = Promise.resolve(200);

let second_promise = Promise.reject("Rejected Promise");

let third_promise = new Promise((resolve, reject) => {
    setTimeout(() => resolve(500), 100)
});

let result =
    Promise.allSettled([first_promise, second_promise, third_promise]);
result.then((value) => console.log(value));

// This code is contributed by Aman Singla....

Output:

[
  { status: 'fulfilled', value: 200 },
  { status: 'rejected', reason: 'Rejected Promise' },
  { status: 'fulfilled', value: 500 }
]

Supported Browsers:

• Google Chrome 76 and above
• Edge 79 and above
• Mozilla Firefox 71 and above
• Opera 63 and above
• Safari 13 and above
• Internet Explorer not supported