JavaScript async and await

Written by Swapnil RajaPublished 24 Aug 2026

async and await let you write asynchronous code that reads like ordinary code.

await pauses inside an async function until a promise settles.

Nothing else is blocked while it waits.

Example

javascript

function delay(value) {
  return new Promise(function (resolve) {
    setTimeout(function () {
      resolve(value);
    }, 10);
  });
}

async function run() {
  const name = await delay("Ada");
  console.log("got " + name);
}

run();

PreviousJavaScript Promise Errors NextJavaScript async Error Handling

Example

javascript

function delay(value) {
  return Promise.resolve(value);
}

async function withAwait() {
  const a = await delay("one");
  const b = await delay(a + " two");
  console.log(b);
}

withAwait();

Example

javascript

function double(n) {
  return Promise.resolve(n * 2);
}

async function run() {
  let total = 0;
  for (const n of [1, 2, 3]) {
    total += await double(n);
  }
  console.log(total);
}

run();

Complete Example

html

<!DOCTYPE html>
<html>
<head>
  <title>JavaScript async and await</title>
</head>
<body>

  <h1>async and await</h1>

  <p id="out">Loading...</p>

  <script>
    function loadUser() {
      return new Promise(function (resolve) {
        setTimeout(function () {
          resolve("Ada Lovelace");
        }, 1000);
      });
    }

    async function show() {
      const name = await loadUser();
      document.getElementById("out").textContent = "Welcome, " + name;
    }

    show();
  </script>

</body>
</html>

JavaScript async and await

Example

async and await

Syntax

An async Function Returns a Promise

Example

The Same Work, Two Ways

Example

Waiting in a Loop

Example

Forgetting await

Example

It Still Does Not Block

Example

Complete Example

Try It Yourself

Important Points

Conclusion