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Async / Await

Write asynchronous code that reads like synchronous code.

1. Explanation

Mark a function with 'async' to make it return a Promise. Inside, use 'await' before a Promise to pause execution until it resolves. Wrap awaits in try/catch to handle errors. Cleaner than .then chains for sequential async work.

2. Example

Try it yourself

function wait(ms) {
  return new Promise(r => setTimeout(r, ms));
}

async function run() {
  console.log("start");
  await wait(500);
  console.log("after 0.5s");
  await wait(500);
  console.log("done");
}

run();

Console

Click Run to see output.

3. Expected output

output

start
after 0.5s
done

4. Common mistakes

✗Forgetting 'await' — the function returns a pending promise
✗Awaiting in a loop when Promise.all would parallelise
✗Using await at the top level outside a module that supports it

5. Practice questions

Convert a .then chain to async/await
Use try/catch around an awaited rejection
Use Promise.all with map to fetch many URLs in parallel

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