Promise.allSettled

mediumcodingJavaScriptPromises~25 min

Asked at Google, Meta, Amazon

Overview

Implement promiseAllSettled(promises) that waits for all promises and returns their outcomes as {status, value} or {status, reason}.

Examples

await promiseAllSettled([Promise.resolve(1), Promise.reject('err')]);
// [{status:'fulfilled',value:1}, {status:'rejected',reason:'err'}]

Solution

Reveal solution

function promiseAllSettled(promises) {
  return Promise.all(
    Array.from(promises).map(p =>
      Promise.resolve(p)
        .then(value => ({ status: 'fulfilled', value }))
        .catch(reason => ({ status: 'rejected', reason }))
    )
  );
}

promise-all-settled.js

Promise.allSettled

mediumcodingJavaScriptPromises

Overview

Implement promiseAllSettled(promises) that waits for all promises and returns their outcomes as {status, value} or {status, reason}.

Examples

await promiseAllSettled([Promise.resolve(1), Promise.reject('err')]);
// [{status:'fulfilled',value:1}, {status:'rejected',reason:'err'}]

Solution

Reveal solution

function promiseAllSettled(promises) {
  return Promise.all(
    Array.from(promises).map(p =>
      Promise.resolve(p)
        .then(value => ({ status: 'fulfilled', value }))
        .catch(reason => ({ status: 'rejected', reason }))
    )
  );
}

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