Await keyword behavior in Javascript - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of async function with await

What is the output of this code snippet?

Javascript

async function test() {
  const result = await Promise.resolve('Hello');
  console.log(result);
}
test();

A undefined

B Promise { 'Hello' }

C Hello

D SyntaxError

💡 Hint

Remember that await unwraps the resolved value of a Promise.

The await keyword waits for the Promise to resolve and returns the resolved value, which is 'Hello'. So console.log prints 'Hello'.

❓ Predict Output

intermediate

Await with non-Promise value

What will this code output?

Javascript

async function example() {
  const val = await 42;
  console.log(val);
}
example();

A Promise { 42 }

B 42

C undefined

D TypeError

💡 Hint

Await can be used with non-Promise values too.

Await treats non-Promise values as resolved Promises and returns the value directly. So val is 42.

❓ Predict Output

advanced

Await inside non-async function

What happens when this code runs?

Javascript

function test() {
  const result = await Promise.resolve('Done');
  console.log(result);
}
test();

A Promise { 'Done' }

B Done

C ReferenceError

D SyntaxError

💡 Hint

Await can only be used inside async functions or modules.

Using await inside a regular function causes a SyntaxError because await is only valid inside async functions or top-level modules.

❓ Predict Output

advanced

Order of execution with await

What is the order of console output when this code runs?

Javascript

async function run() {
  console.log('Start');
  await new Promise(resolve => setTimeout(resolve, 0));
  console.log('End');
}
run();
console.log('After run');

A Start\nAfter run\nEnd

B Start\nEnd\nAfter run

C After run\nStart\nEnd

D End\nStart\nAfter run

💡 Hint

Await pauses the async function but does not block the main thread.

The function logs 'Start', then awaits a Promise that resolves after 0ms, so the main thread continues and logs 'After run' before 'End'.

🧠 Conceptual

expert

Await behavior with rejected Promise

What happens when this code runs?

Javascript

async function test() {
  try {
    await Promise.reject('Error occurred');
  } catch (e) {
    console.log('Caught:', e);
  }
}
test();

A Caught: Error occurred

B Uncaught (in promise) Error occurred

C SyntaxError

D undefined

💡 Hint

Await throws if the Promise rejects, so catch block runs.

The rejected Promise causes await to throw, which is caught by the catch block, logging 'Caught: Error occurred'.