JavaScript › Async Iterators & Streams

How do you add a timeout to an async iterator's next() call?

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Answer

Race the iterator's next() Promise against a Promise that rejects after a timeout using Promise.race(), so a slow or stalled source doesn't hang your consumer forever.

function withTimeout(promise, ms) {
  const timeout = new Promise((_, reject) =>
    setTimeout(() => reject(new Error('timeout')), ms));
  return Promise.race([promise, timeout]);
}
const { value } = await withTimeout(iterator.next(), 5000);

Real-world example Cutting off a stalled WebSocket or SSE connection after a set idle period.

Common follow-ups: How would you also clean up the timer if the original promise wins the race?

Error Handling