Description

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Intermediate · 12 min

Promises and async/await

Wait for asynchronous results and handle rejected promises.

Await a result

An async function returns a promise. await pauses that function until the promise settles; it does not block the browser thread. The playground runs each program as a module, where top-level await is available.

async function getName() { return "Ada"; }
const name = await getName();
console.log(name);

Output

Ada

Catch a rejection

A rejected promise becomes a thrown error at await. Use try/catch around the awaited operation when you can recover. These examples use local promises instead of network requests.

async function load() { throw new Error("Unavailable"); }
try { await load(); } catch (error) { console.log(error.message); }

Output

Unavailable

Put it into practice

  1. Predict each result before running the example.
  2. Complete the coding task, then explain why your solution works.

Try it yourself

Code runs on this device. When you are signed in, drafts sync to your account.

Wait for the total

Await calculate() before displaying total.

Practice