Async/Await — Series 3

Preview — 3 of 10 questions

What is logged?

javascript

const delay = (ms, v) => new Promise((r) => setTimeout(() => r(v), ms));

Promise.any([Promise.reject(new Error('a')), delay(10, 'b')])
  .then((v) => console.log('any:', v));

Promise.any([Promise.reject(new Error('x')), Promise.reject(new Error('y'))])
  .catch((e) => console.log(e.constructor.name, e.errors.length));

Aany: a, then Error 2

BAggregateError 2, then any: b

CAggregateError 2, then any: b — the first rejection is ignored because a later input fulfils

Dany: b, then TypeError 2

What is logged?

javascript

Promise.allSettled([Promise.resolve(1), Promise.reject(new Error('no'))]).then((rs) => {
  console.log(JSON.stringify(rs.map((r) => (r.status === 'fulfilled' ? r.value : r.reason.message))));
});

A[1,"no"]

B[1]

C["fulfilled","rejected"]

D[1,null]

What is logged?

javascript

const delay = (ms, v) => new Promise((r) => setTimeout(() => r(v), ms));

async function run() {
  const start = Date.now();
  const [a, b] = await Promise.all([delay(50, 'a'), delay(50, 'b')]);
  console.log(a + b, Date.now() - start < 90);
}
run();

Aab false

Bba true

Cundefinedundefined true

Dab true

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