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

Async/await is a powerful feature in JavaScript that simplifies asynchronous code, making it cleaner and easier to read. However, improper usage can lead to several anti-patterns that can hurt performance, readability, and maintainability. This post outlines ten common async/await anti-patterns and provides solutions to avoid them.

1. Neglecting Error Handling

Async functions can throw errors, just like synchronous functions. Failing to catch these errors can lead to unhandled promise rejections and application crashes.

Anti-Pattern:

async function fetchData() {
  const response = await fetch('some-url');
  const data = await response.json();
  return data;
}

Solution:
Use try...catch blocks to handle potential errors.

async function fetchData() {
  try {
    const response = await fetch('some-url');
    const data = await response.json();
    return data;
  } 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 in Synchronous Code

Async/await is designed for asynchronous operations. Using it unnecessarily in synchronous contexts adds unnecessary complexity.

Anti-Pattern:

async function add(a, b) {
  return a + b;
}

Solution: Use a regular synchronous function for synchronous operations.

function add(a, b) {
  return a + b;
}

3. Ignoring await in Promise Chains

Forgetting await within a chain of asynchronous operations will prevent proper sequencing and error handling.

Anti-Pattern:

async function processData() {
  const data1 = await fetchData1();
  const data2 = fetchData2(); // Missing await!
  // data2 might not be resolved when this line runs
  return data1 + data2; 
}

Solution: await each promise in the chain.

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

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

Deeply nested async/await calls create a difficult-to-read and maintainable code structure.

Anti-Pattern:

async function nestedCalls() {
  const result1 = await func1();
  const result2 = await func2(result1);
  const result3 = await func3(result2);
  // ... and so on
}

Solution: Use techniques like Promise.all or refactoring into smaller, more manageable functions.

async function parallelCalls() {
  const [result1, result2] = await Promise.all([func1(), func2()]);
  const result3 = await func3(result2);
}

5. Ignoring Promise Resolution/Rejection

Failing to handle promise resolution or rejection leads to silent failures and unexpected behavior.

Anti-Pattern:

fetchData().then(() => {}); //No error handling or success handling 

Solution: Always handle both resolution and rejection in .then() or use async/await with try-catch.

6. Blocking the Event Loop

Long-running operations within async functions can block the event loop, causing UI freezes and poor performance. Use Web Workers for CPU-bound tasks.

7. Unnecessary Async Functions

Avoid wrapping simple synchronous operations in async functions.

8. Forgetting to Return Promises

Async functions should generally return a Promise.

9. Improper use of Promise.all

Using Promise.all with unrelated or independent asynchronous operations can impact performance.

10. Inconsistent Error Handling

Maintain consistency in your error handling strategy throughout your codebase.

Conclusion

Async/await is a powerful tool, but proper usage is crucial. By avoiding these common anti-patterns, you can write more efficient, readable, and maintainable asynchronous JavaScript code. Remember to prioritize error handling, avoid unnecessary complexity, and use the appropriate techniques for managing asynchronous operations efficiently.