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Implement promiseRetry(fn, retries, delay) with exponential backoff

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01

Understand the problem

Create a retry utility that calls an async fn up to retries times with exponential backoff. Support abort on certain errors.

retrypromiseexponential-backoff
02

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Sketch your approach before reading the solution — that's what interviews test.

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03

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Approach: Loop with try/catch, await sleep(delay * 2**attempt). Optionally check shouldRetry(err).

function sleep(ms) { return new Promise(r => setTimeout(r, ms)); }
async function promiseRetry(fn, { retries = 3, delay = 100, factor = 2, shouldRetry = () => true } = {}) {
  let lastError;
  for

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