Running scripts with node command in Node.js - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

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

Consider the following Node.js script saved as script.js. What will be printed to the console when you run node script.js?

Node.js

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

A undefined

B Hello from Node.js!

C SyntaxError

D ReferenceError

💡 Hint

Think about what console.log does in Node.js.

The script prints the string inside console.log to the console when run with node.

❓ Predict Output

intermediate

What happens if you run a script with a syntax error?

Given this Node.js script saved as error.js, what will happen when you run node error.js?

Node.js

console.log('Missing quote);

A ReferenceError: Missing quote is not defined

B undefined

C No output, script runs silently

D SyntaxError: Invalid or unexpected token

💡 Hint

Look carefully at the quotes in the code.

The missing closing quote causes a syntax error preventing the script from running.

❓ component_behavior

advanced

What will be the output of this asynchronous Node.js script?

Examine the following script saved as async.js. What will be printed when running node async.js?

Node.js

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

A

Start
End
Timeout

B

Start
Timeout
End

C

Timeout
Start
End

D

End
Start
Timeout

💡 Hint

Remember how setTimeout works with zero delay.

setTimeout schedules the callback after the current call stack finishes, so 'Timeout' prints last.

🔧 Debug

advanced

Why does this Node.js script throw an error when run?

Look at this script saved as errorCheck.js. When running node errorCheck.js, it throws an error. What is the cause?

Node.js

const fs = require('fs');
fs.readFile('nonexistent.txt', (err, data) => {
  if (err) throw err;
  console.log(data.toString());
});

A Throws error because require is not defined

B No error, prints empty string

C Throws error because the file does not exist

D Throws error because readFile is synchronous

💡 Hint

Check what happens when reading a file that is missing.

The callback receives an error object because the file is missing, and the script throws it.

📝 Syntax

expert

Which option correctly runs a Node.js script with ES module syntax?

You have a script module.mjs using ES module syntax with import. How do you run it with Node.js?

Node.js

import fs from 'fs';
console.log('Module loaded');

A node module.mjs

B node --require module.mjs

C node --experimental-modules module.mjs

D node module.js

💡 Hint

Modern Node.js supports ES modules with .mjs extension by default.

Node.js runs .mjs files as ES modules without extra flags in recent versions.