Async/Await — Series 2

Preview — 3 of 10 questions

What is logged?

javascript

const fast = new Promise((resolve) => setTimeout(() => resolve('fast'), 10));
const slow = new Promise((resolve) => setTimeout(() => resolve('slow'), 50));

Promise.race([slow, fast]).then((result) => console.log(result));

A"slow"

B"fast"

C["fast", "slow"]

DTypeError: Promise.race is not a function

What is logged?

javascript

const p1 = Promise.resolve('ok');
const p2 = Promise.reject(new Error('fail'));

Promise.allSettled([p1, p2]).then((results) => {
  console.log(results.map((r) => r.status));
});

A["ok", "fail"]

B["fulfilled"]

CPromise.allSettled rejects immediately because p2 rejected

D["fulfilled", "rejected"]

What is logged? (Assume timer delays run close to their specified values.)

javascript

function delay(ms, val) {
  return new Promise((resolve) => setTimeout(() => resolve(val), ms));
}

async function run() {
  const start = Date.now();
  const results = [];
  for (const ms of [50, 50, 50]) {
    results.push(await delay(ms, ms));
  }
  console.log(results);
  console.log(Date.now() - start >= 140);
}

run();

A[50, 50, 50], true

B[50, 50, 50], false

C[150]

DTypeError: results.push is not a function

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