JavaScript › Error Handling

How do you implement a retry-with-backoff pattern around a function that might throw?

Advanced

Answer

Wrap the call in a loop with a try/catch; on failure, wait an increasing delay (e.g. exponential backoff) before retrying, up to a maximum attempt count, then re-throw the final error if all attempts fail.

async function retry(fn, attempts = 3, delay = 500) {
  for (let i = 0; i < attempts; i++) {
    try {
      return await fn();
    } catch (err) {
      if (i === attempts - 1) throw err;
      await new Promise(r => setTimeout(r, delay * 2 ** i));
    }
  }
}

Real-world example Retrying a flaky network request up to three times with increasing delays before giving up and showing an error.

Common follow-ups: How would you avoid retrying on errors that are clearly not transient, like a 404?

Promises & async/await