Running JavaScript using Node.js - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple Node.js script

What is the output when running this Node.js script?

Javascript

console.log('Hello from Node.js!');

A ReferenceError

B undefined

C SyntaxError

D Hello from Node.js!

💡 Hint

Look at what console.log prints to the terminal.

console.log prints the string to the console, so the output is exactly the string inside the quotes.

❓ Predict Output

intermediate

Understanding asynchronous behavior in Node.js

What will be the output order when running this Node.js code?

Javascript

console.log('Start');
setTimeout(() => console.log('Timeout'), 0);
console.log('End');

A

End
Start
Timeout

B

Start
End
Timeout

C

Timeout
Start
End

D

Start
Timeout
End

💡 Hint

setTimeout with 0 delay runs after the current call stack is empty.

The synchronous logs run first: 'Start' then 'End'. The setTimeout callback runs last.

❓ Predict Output

advanced

Output of a Node.js script using process.argv

What will be the output if you run this script with: node script.js hello world?

Javascript

console.log(process.argv.slice(2));

A ["hello", "world"]

B ["node", "script.js", "hello", "world"]

C SyntaxError

D undefined

💡 Hint

process.argv contains command line arguments; slice(2) skips the first two.

process.argv is an array of command line arguments. The first two are node executable and script path.

❓ Predict Output

advanced

Error type when requiring a non-existent module

What error will Node.js throw when running this code?

Javascript

require('nonexistent-module');

A Error: Cannot find module 'nonexistent-module'

B ReferenceError: require is not defined

C TypeError: require is not a function

D SyntaxError: Unexpected token

💡 Hint

Node.js throws an error if a required module is missing.

The error message clearly states the module cannot be found.

❓ Predict Output

expert

Output of a Node.js script using top-level await

What will this script output when run with Node.js 20+?

Javascript

const wait = ms => new Promise(resolve => setTimeout(resolve, ms));

await wait(100);
console.log('Done waiting');

A ReferenceError: wait is not defined

B SyntaxError: await is only valid in async function

C Done waiting

D TypeError: wait is not a function

💡 Hint

Node.js 20+ supports top-level await in modules.

Top-level await pauses execution until the promise resolves, then logs the message.