// Created on savesnippets.com · https://savesnippets.com/2syFiadkwIxlZD
async function fetchRetry(url, options = {}, retries = 3, backoff = 300) {
  for (let i = 0; i < retries; i++) {
    try {
      const res = await fetch(url, options);
      if (res.ok) return res;
      if (res.status < 500) throw new Error(`HTTP ${res.status}`); // don't retry 4xx
    } catch (err) {
      if (i === retries - 1) throw err;
    }
    await new Promise((r) => setTimeout(r, backoff * 2 ** i));
  }
}

// Usage
const res  = await fetchRetry('/api/data', {}, 3, 500);
const data = await res.json();