What is Node.js in Node.js - Practice Questions & Exercises

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is Node.js primarily used for?

Node.js is a popular tool in software development. What is its main use?

A Writing HTML code to structure web pages.

B Running JavaScript code on the server side to build web servers and backend services.

C Designing database schemas and managing data storage.

D Creating stylesheets for web pages to control layout and colors.

💡 Hint

Think about where JavaScript usually runs and what Node.js changes about that.

Node.js allows JavaScript to run outside the browser, mainly on servers, enabling backend development.

❓ component_behavior

intermediate

What does this Node.js code output?

Consider this Node.js code snippet. What will it print to the console?

Node.js

console.log(typeof process);

A "object"

B "undefined"

C "function"

D "string"

💡 Hint

Think about what process is in Node.js.

The process is a global object in Node.js representing the current process, so its type is "object".

📝 Syntax

advanced

Which option correctly imports the 'fs' module in Node.js ES modules?

Node.js supports different module systems. Which code correctly imports the built-in 'fs' module using ES module syntax?

A import * as fs from 'fs';

B const fs = require('fs');

C import { fs } from 'fs';

D import fs from 'fs';

💡 Hint

ES modules use import statements. Think about how to import all exports as one object.

In ES modules, import * as fs from 'fs'; imports the entire module as an object named fs.

❓ state_output

advanced

What is the output of this asynchronous Node.js code?

Look at this Node.js code using setTimeout. What will it print?

Node.js

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

A "Start" then "Inside timeout" then "End"

B "Inside timeout" then "Start" then "End"

C "Start" then "End" then "Inside timeout"

D "End" then "Start" then "Inside timeout"

💡 Hint

Remember how JavaScript handles asynchronous callbacks with the event loop.

Even with zero delay, setTimeout callbacks run after the current code finishes, so 'End' prints before 'Inside timeout'.

🔧 Debug

expert

Which option causes a runtime error in this Node.js code?

Given this code snippet, which option will cause a runtime error when executed?

Node.js

import * as fs from 'fs';

fs.readFile('nonexistent.txt', 'utf8', (err, data) => {
  if (err) throw err;
  console.log(data);
});

A The code will silently fail without any output or error.

B The code will print an empty string because the file is empty.

C The code will print 'undefined' because the callback parameters are incorrect.

D The file 'nonexistent.txt' does not exist, so the callback receives an error and throws it, causing a runtime error.

💡 Hint

Think about what happens when you try to read a file that does not exist.

Trying to read a missing file causes an error passed to the callback. Throwing that error crashes the program.