Mastering Async/Await in JavaScript: 7 Mistakes to Avoid

Async/await changed the way we write JavaScript. No more messy callbacks, no endless .then() chains. But it’s not magic. Misuse it, and you’ll still end up with bugs, performance issues, and confusion.

Let’s walk through 7 async/await mistakes I see all the time, and how to avoid them.

1. Forgetting to await

async function fetchData() {
  const data = getUserData(); // missing await
  console.log(data);
}

➡️ Without await, data is a Promise, not the actual result. ✅ Always await async functions unless you really want the raw Promise.

2. Using await inside loops

for (let user of users) {
  await sendEmail(user); // slow, runs one by one
}

➡️ This runs sequentially. ✅ Use Promise.all to run tasks in parallel:

await Promise.all(users.map(sendEmail));

3. Forgetting error handling

const data = await fetch("/api"); // what if it fails?

✅ Wrap in try/catch:

try {
  const res = await fetch("/api");
  const data = await res.json();
} catch (err) {
  console.error("API error:", err);
}

4. Mixing then() and await everywhere

You’ll sometimes see:

const data = await fetch("/api").then(r => r.json());

It works, but it’s confusing. Stick to one style: async/await.

5. Not returning inside async functions

    async function getData() {
      await fetch("/api");
      // forgot to return result
    }

✅ Always return values explicitly.

6. Blocking code before await

const res = await fetch("/slow-api");
expensiveCalculation(); // runs after slow network

➡️ Expensive synchronous work blocks event loop. ✅ Offload heavy work to workers or break into smaller tasks.

7. Not knowing when to skip await

Sometimes you don’t want to wait:

async function notify() {
  sendAnalytics(); // fire and forget
}

✅ That’s fine, just be intentional.

🚀 Key Takeaways

Async/await makes code more readable, but readability doesn’t equal correctness. Remember:

  • Always await async results.
  • Avoid sequential awaits in loops.
  • Handle errors with try/catch.
  • Be consistent with style.

Once these become habits, async code feels natural and reliable.

🌱 Final Thoughts

Writing async code is less about syntax and more about discipline. Master these patterns, and you’ll avoid 90% of async bugs in JavaScript.