Q86- How would you implement a retry mechanism for an API call?

A retry mechanism automatically retries a failed API call a certain number of times, often with a delay, to handle temporary network issues or server errors.

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1️⃣ Basic Retry Function

async function fetchWithRetry(url, options = {}, retries = 3, delay = 1000) {
  for (let i = 0; i <= retries; i++) {
    try {
      const response = await fetch(url, options);
      if (!response.ok) {
        throw new Error(`HTTP error! status: ${response.status}`);
      }
      return await response.json(); // success
    } catch (err) {
      if (i < retries) {
        console.log(`Retrying... attempt ${i + 1}`);
        await new Promise(res => setTimeout(res, delay)); // wait before retry
      } else {
        throw err; // all retries failed
      }
    }
  }
}

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2️⃣ Usage Example

fetchWithRetry("https://api.example.com/data", {}, 3, 1000)
  .then(data => console.log("Data:", data))
  .catch(err => console.error("Failed after 3 retries:", err));

✅ What happens:

1. Try API call
2. If it fails → wait 1s → retry
3. Repeat up to 3 times
4. If all fail → throw error

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3️⃣ Optional Enhancements

• Exponential Backoff: Increase delay after each retry

await new Promise(res => setTimeout(res, delay * Math.pow(2, i)));

• Retry Only on Certain Errors:

if (response.status >= 500) { /* retry */ }

• Abort on Certain Errors: Stop retrying if client error (400–499)

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⚡ In short:

A retry mechanism attempts an API call multiple times with optional delay, handling temporary failures gracefully. Using async/await with a for loop and setTimeout is the simplest and cleanest approach.