🔄 Promise Retry Implementation

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Promise retry is a resilience pattern that automatically retries a failed async operation a specified number of times before giving up. This is essential for handling transient network failures, rate limits, or intermittent service unavailability.

✅ Implementation

function retry(fn, retries = 3, delay = 0) {
  return new Promise((resolve, reject) => {
    const attempt = (n) => {
      fn()
        .then(resolve)
        .catch((err) => {
          if (n === 0) return reject(err);
          setTimeout(() => attempt(n - 1), delay);
        });
    };
    attempt(retries);
  });
}

🧪 Example:

let counter = 0;
const unstableTask = () => {
  return new Promise((res, rej) => {
    counter++;
    if (counter < 3) rej("fail " + counter);
    else res("success on attempt " + counter);
  });
};

retry(unstableTask, 5, 500)
  .then(console.log)
  .catch(console.error);

✅ Features:

fn is retried up to retries times.
Optional delay (ms) between retries.
Stops on first success.
Rejects with final error if all fail.

Quick Quiz

Test your understanding with 3 quick questions

Q1In the retry implementation, what happens when a retry succeeds?

Q2Why must the first argument to retry() be a function that returns a promise, rather than a promise itself?

Q3What is a common real-world use case for promise retry?

✅ Implementation

function retry(fn, retries = 3, delay = 0) {
  return new Promise((resolve, reject) => {
    const attempt = (n) => {
      fn()
        .then(resolve)
        .catch((err) => {
          if (n === 0) return reject(err);
          setTimeout(() => attempt(n - 1), delay);
        });
    };
    attempt(retries);
  });
}

🧪 Example:

let counter = 0;
const unstableTask = () => {
  return new Promise((res, rej) => {
    counter++;
    if (counter < 3) rej("fail " + counter);
    else res("success on attempt " + counter);
  });
};

retry(unstableTask, 5, 500)
  .then(console.log)
  .catch(console.error);

✅ Features:

fn is retried up to retries times.

Optional delay (ms) between retries.

Stops on first success.

Rejects with final error if all fail.

Quick Quiz

Test your understanding with 3 quick questions

Q1In the retry implementation, what happens when a retry succeeds?

Q2Why must the first argument to retry() be a function that returns a promise, rather than a promise itself?

Q3What is a common real-world use case for promise retry?

🔄 Promise Retry Implementation

✅ Implementation

🧪 Example:

✅ Features:

Continue Reading

🛑 AbortController: Canceling Async Operations in JavaScript

🔒 Closures in JavaScript — The Complete Guide

📦 Understanding ES6 Modules in JavaScript

🔄 Promise Retry Implementation

✅ Implementation

🧪 Example:

✅ Features:

Continue Reading

🛑 AbortController: Canceling Async Operations in JavaScript

🔒 Closures in JavaScript — The Complete Guide

📦 Understanding ES6 Modules in JavaScript