TS Samples

wait-for.ts

console.clear();
const appStart = Date.now();

const delay = async (delayMs: number) => new Promise(res => setTimeout(res, delayMs));

const waitFor = async (checkFn: () => Promise<boolean>, maxWaitMs = 5000, pollIntervalMs = 250): Promise<void> => {
  const start = Date.now();  

  // const waitForIt = async (start: number): Promise<void> => {
  //   const check = await checkFn();
  //   const elapsedMs = Date.now() - start;

  //   console.log('waitForIt', {
  //     check,
  //     start,
  //     elapsedMs,
  //     maxWaitMs,
  //     timeout: elapsedMs > maxWaitMs,
  //     pollIntervalMs,
  //   })
  //   if (check === true) return;
  //   if (elapsedMs > maxWaitMs) throw new Error('Max wait time reached');

  //   await delay(pollIntervalMs);
  //   return await waitForIt(start);
  // }

  const waitForCheck = async (): Promise<void> => {
    if (await checkFn() === true) return;
    if (Date.now() - start > maxWaitMs) throw new Error('Max wait time reached');

    await delay(pollIntervalMs);
    return await waitForCheck();
  }

  return await waitForCheck();
}

let x = 3;
const testCheck = async () => {
  console.log('Waiting for a second', x);
  await new Promise(res => setTimeout(res, 2500));
  console.log('Done waiting', x);

  return --x === 0;
}

(async () => {
  try {
    await waitFor(testCheck);
    console.log('YYYYYYYYYYYYYYYYYYYY Check passed');
  } catch(err) {
    console.log('XXXXXXXXXXXXXXXXXXXX Check timed out');
  };
  console.log({ Finished: Date.now() - appStart });
})();