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.