Common Async Patterns

Async Patterns

Retry, memoization (cache), and sequential processing are recurring async patterns worth knowing.

Example

// Retry with exponential back-off
async function withRetry(fn, retries = 3, delay = 500) {
  try { return await fn(); }
  catch (e) {
    if (retries === 0) throw e;
    await new Promise(r => setTimeout(r, delay));
    return withRetry(fn, retries - 1, delay * 2);
  }
}
// Memoize async
const memo = new Map();
const cachedFetch = url => memo.get(url) ?? memo.set(url, fetch(url).then(r => r.json())).get(url);

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Pro Tip

Cache the Promise, not the resolved value — callers await the same Promise without duplicate fetches.

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