Async/await syntax in Node.js - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of async function with await

What will be the output of this Node.js code snippet?

Node.js

async function fetchData() {
  return 'data';
}

async function main() {
  const result = await fetchData();
  console.log(result);
}

main();

A Error: await is only valid in async function

B Promise { 'data' }

C undefined

D data

💡 Hint

Remember that await unwraps the resolved value of a promise inside an async function.

The async function fetchData returns a resolved promise with 'data'. Await unwraps it, so console.log prints 'data'.

❓ component_behavior

intermediate

Behavior of async function returning a rejected promise

What happens when this async function is called without a try/catch block?

Node.js

async function fail() {
  throw new Error('fail');
}

fail();

A The error is silently ignored

B The program crashes immediately

C A rejected promise is returned but no error is thrown synchronously

D The error is logged to console automatically

💡 Hint

Async functions always return promises, even when throwing errors.

Throwing inside async returns a rejected promise. Without await or catch, no synchronous error occurs.

📝 Syntax

advanced

Identify the incorrect usage in async/await

Which option contains incorrect usage of async/await?

Node.js

async function test() {
  const data = await fetchData();
  return data;
}

A const data = await fetchData;

B const data = await fetchData();

C await fetchData();

D async function test() { const data = await fetchData(); return data; }

💡 Hint

Remember that await expects a function call returning a promise, not the function itself.

Option A misses parentheses after fetchData, so await is applied to the function object instead of calling it.

🔧 Debug

advanced

Why does this async function never resolve?

Consider this code. Why does the console.log never run?

Node.js

async function waitForever() {
  await new Promise(() => {});
  console.log('Done');
}

waitForever();

A The promise never resolves or rejects, so await waits forever

B The console.log is unreachable due to syntax error

C The function throws an error before console.log

D The await keyword is used incorrectly

💡 Hint

What happens if a promise never settles?

The promise passed to await never calls resolve or reject, so await waits forever and console.log never runs.

🧠 Conceptual

expert

Effect of missing await in async function call

What is the value of variable result after running this code?

Node.js

async function getValue() {
  return 42;
}

const result = getValue();

A 42

B Promise { 42 }

C undefined

D Error: Missing await

💡 Hint

Async functions always return promises, even if you don't use await.

Calling an async function returns a promise immediately. Without await, result is that promise, not the resolved value.