JavaScript’s Top 10 Async/Await Anti-Patterns (and How to Avoid Them)

Async/await is a powerful feature in JavaScript that makes asynchronous code easier to read and write. However, improper use can lead to several anti-patterns that can make your code harder to maintain, debug, and scale. This post outlines ten common async/await anti-patterns and provides solutions to avoid them.

1. Neglecting Error Handling

One of the most common mistakes is forgetting to handle potential errors within your async functions. Async functions can throw errors just like synchronous functions. Ignoring them can lead to silent failures.

async function fetchData() {
  const response = await fetch('/api/data');
  return response.json(); // Error if fetch fails
}

Solution: Always use try...catch blocks to handle potential errors.

async function fetchData() {
  try {
    const response = await fetch('/api/data');
    return response.json();
  } catch (error) {
    console.error('Error fetching data:', error);
    // Handle the error appropriately, e.g., return a default value or throw a custom error
    return null;
  }
}

2. Overusing Async/Await for Synchronous Operations

Async/await adds overhead. Don’t use it for operations that don’t involve asynchronous actions (e.g., simple calculations).

Solution: Use regular synchronous functions for synchronous operations.

3. Ignoring await in a chain of Promises

When calling multiple async functions sequentially, forgetting to await each one results in the results not being handled correctly. The code will continue execution before the promises resolve.

Solution: Always use await when you need the result of an asynchronous operation before proceeding.

async function processData() {
  const data1 = await fetchData1();
  const data2 = await fetchData2(data1);
  const result = await process(data2);
  return result;
}

4. Unhandled Promise Rejections

Unhandled promise rejections can lead to unexpected behavior and crashes. Even with try...catch, errors within promises that aren’t handled appropriately can escape.

Solution: Use .catch() on promises and a global unhandled rejection handler (e.g., process.on('unhandledRejection', ...) in Node.js).

5. Nested Async/Await Calls (Pyramid of Doom)

Deeply nested async/await calls can lead to the dreaded “pyramid of doom”. This makes the code difficult to read and understand.

Solution: Use techniques like helper functions or promise chaining to flatten the structure.

6. Blocking the Event Loop

Long-running synchronous operations within an async function can block the event loop, causing performance issues and unresponsiveness.

Solution: Offload long-running tasks to Web Workers or use techniques like chunking to prevent blocking.

7. Ignoring Cancellation

Long running asynchronous operations should allow for cancellation. Ignoring this can waste resources and time.

Solution: Use mechanisms like AbortController to allow cancellation of requests.

8. Forgetting to Return Promises

Async functions that don’t return a promise can break the asynchronous chain.

Solution: Always ensure your async functions return a promise.

9. Mixing Async/Await with Callbacks

Mixing async/await with traditional callbacks makes code harder to read and maintain.

Solution: Use a consistent asynchronous programming style throughout your project.

10. Insufficient Logging and Debugging

Debugging asynchronous code can be challenging. Lack of logging makes it harder to track down errors.

Solution: Use logging statements throughout your async functions to trace execution flow and identify issues.

Conclusion

Async/await is a powerful tool, but it’s crucial to understand and avoid these common pitfalls. By adhering to best practices, you can write cleaner, more maintainable, and more efficient asynchronous JavaScript code.