JavaScript Async/Await Best Practices

Modern JavaScript uses async/await for handling asynchronous operations. Here are the best practices:

1. Always Handle Errors

async function fetchUserData(userId) {
    try {
        const response = await fetch(`/api/users/${userId}`);
        const data = await response.json();
        return data;
    } catch (error) {
        console.error('Failed to fetch user:', error);
        throw error;
    }
}

2. Parallel Execution

Don't await in sequence when you can run in parallel:

// ❌ Slow - Sequential
const user = await fetchUser();
const posts = await fetchPosts();
const comments = await fetchComments();

// ✅ Fast - Parallel
const [user, posts, comments] = await Promise.all([
    fetchUser(),
    fetchPosts(),
    fetchComments()
]);

3. Promise.allSettled for Independent Operations

const results = await Promise.allSettled([
    fetchUser(),
    fetchPosts(),
    fetchComments()
]);

results.forEach(result => {
    if (result.status === 'fulfilled') {
        console.log('Success:', result.value);
    } else {
        console.log('Error:', result.reason);
    }
});

4. Avoid Async in Loops

// ❌ Bad
for (const id of userIds) {
    await processUser(id);
}

// ✅ Good
await Promise.all(userIds.map(id => processUser(id)));

Key Takeaways

• Always use try/catch for error handling
• Use Promise.all() for parallel operations
• Consider Promise.allSettled() for independent tasks
• Avoid awaiting inside loops

Async/await makes asynchronous code look synchronous, but understanding Promises is still crucial!