📚 2 min read

Async JavaScript Patterns

Master asynchronous programming in JavaScript with comprehensive patterns and examples.

Core Concepts

• Promises: Understanding the Promise API and its patterns
• Async/Await: Modern asynchronous programming
• Error Handling: Proper error management in async code
• Performance: Optimizing async operations

Available Guides

Promise Patterns

• Custom Promises - Creating custom Promise wrappers
• Promise.all - Parallel execution patterns
• Promise.race - Racing promises
• Promise.any - First success patterns
• Promise.allSettled - Complete settlement patterns
• Promise.finally - Cleanup patterns
• Promisifying - Converting callbacks to promises

Task Management

• Parallel Tasks - Running tasks in parallel
• Sequential Tasks - Running tasks in sequence
• Racing Tasks - Implementing task races

Timer Patterns

• Timer Management - Managing timers effectively
• Custom setTimeout - Custom timeout implementations
• Custom setInterval - Custom interval implementations

Performance

• Auto-Retry - Implementing retry logic
• Batch Throttling - Batch processing
• Debouncing - Debounce implementations
• Throttling - Throttle implementations
• Memoization - Caching results

Quick Examples

// Basic Promise usage
const delay = (ms: number) => new Promise(resolve => setTimeout(resolve, ms));

// Async/Await pattern
async function example() {
  console.log('Start');
  await delay(1000);
  console.log('One second later');
}

// Error handling with retry
async function fetchWithRetry(url: string, retries = 3) {
  for (let i = 0; i < retries; i++) {
    try {
      const response = await fetch(url);
      return await response.json();
    } catch (error) {
      if (i === retries - 1) throw error;
      await delay(1000 * Math.pow(2, i)); // Exponential backoff
    }
  }
}

// Parallel execution
async function fetchAll(urls: string[]) {
  return Promise.all(urls.map(url => fetch(url)));
}

// Race pattern
async function fetchWithTimeout(url: string, timeout: number) {
  return Promise.race([
    fetch(url),
    delay(timeout).then(() => {
      throw new Error('Request timed out');
    })
  ]);
}

Best Practices

1. Error Handling

   • Always handle Promise rejections
   • Use try/catch with async/await
   • Implement proper retry strategies

2. Performance

   • Control concurrency levels
   • Implement timeouts for long operations
   • Use appropriate Promise combinators

3. Resource Management

   • Clean up resources in finally blocks
   • Implement proper cancellation
   • Handle memory leaks

4. Code Organization

   • Keep async functions focused
   • Use meaningful Promise chains
   • Document async behavior </rewritten_file>