How Node.js differs from browser JavaScript in Node.js - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the built-in 'fs' module in Node.js.

Node.js

const fs = require([1]);

Drag options to blanks, or click blank then click option'

A'http'

B'fs'

C'express'

D'path'

Attempts:

3 left

💡 Hint

Common Mistakes

Using browser-specific modules like 'express' instead of 'fs'.

Forgetting to put quotes around the module name.

Node.js uses require to import built-in modules like fs for file system operations.

2fill in blank

medium

Complete the code to create a simple HTTP server in Node.js.

Node.js

const http = require('http');
http.createServer((req, res) => {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello World');
}).[1](3000);

Drag options to blanks, or click blank then click option'

Alisten

Bstart

Copen

Drun

Attempts:

3 left

💡 Hint

Common Mistakes

Using methods like 'start' or 'run' which do not exist on the server object.

Forgetting to call the method with parentheses.

The listen method starts the server on the specified port.

3fill in blank

hard

Fix the error in the code to read a file asynchronously in Node.js.

Node.js

const fs = require('fs');
fs.readFile('example.txt', 'utf8', (err, data) => {
  if (err) throw err;
  console.log([1]);
});

Drag options to blanks, or click blank then click option'

Aexample.txt

Berr

Cfs

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Logging the error object instead of the file content.

Trying to log the module or file name instead of the data.

The callback receives the file content as data, which should be logged.

4fill in blank

hard

Fill both blanks to export a function named 'greet' in Node.js.

Node.js

function greet() {
  console.log('Hello!');
}
module.[1] = [2];

Drag options to blanks, or click blank then click option'

Aexports

Bgreet

Cmodule

Drequire

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'require' instead of 'exports' for exporting.

Assigning the wrong variable to exports.

Use module.exports to export the greet function so other files can use it.

5fill in blank

hard

Fill all three blanks to create a simple Express server that responds with 'Hi' on the root path.

Node.js

const express = require([1]);
const app = express();
app.[2]('/', (req, res) => {
  res.[3]('Hi');
});
app.listen(3000);

Drag options to blanks, or click blank then click option'

A'express'

Bget

Csend

D'http'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'http' instead of 'express' for the module name.

Using 'post' instead of 'get' for the route method.

Using 'write' instead of 'send' to respond.

Import Express with 'express', use get to handle GET requests, and send to send the response.

Practice

1. Which of the following is a key difference between Node.js and browser JavaScript?

easy

A. Browser JavaScript can run server-side code, but Node.js cannot.

B. Browser JavaScript can access databases directly, but Node.js cannot.

C. Node.js runs only inside web pages, while browser JavaScript runs on servers.

D. Node.js can access the file system, but browser JavaScript cannot.

Solution

1. Step 1: Understand environment capabilities

   Node.js runs outside the browser and can access system resources like files.

2. Step 2: Compare browser limitations

   Browser JavaScript runs inside web pages and cannot access the file system for security reasons.

3. Final Answer:

   Node.js can access the file system, but browser JavaScript cannot. -> Option D

4. Quick Check:

   File system access = Node.js only [OK]

Hint: Remember: Node.js can read files; browsers cannot [OK]

Common Mistakes:

• Thinking browser JavaScript can access local files directly
• Confusing server-side and client-side roles
• Assuming Node.js runs inside web pages

2. Which syntax correctly imports the built-in 'fs' module in Node.js?

easy

A. import fs from 'fs';

B. const fs = require('fs');

C. let fs = import('fs');

D. var fs = fetch('fs');

Solution

1. Step 1: Identify Node.js import syntax

   Node.js traditionally uses CommonJS syntax: const fs = require('fs');.

2. Step 2: Check other options

   import fs from 'fs'; is ES module syntax, which requires special setup; var fs = fetch('fs'); and let fs = import('fs'); are invalid for module import.

3. Final Answer:

   const fs = require('fs'); -> Option B

4. Quick Check:

   CommonJS require() syntax = const fs = require('fs'); [OK]

Hint: Use require() to import built-in modules in Node.js [OK]

Common Mistakes:

• Using browser import syntax without Node.js ES module setup
• Confusing fetch() with module import
• Trying to use import() as a variable assignment

3. What will the following Node.js code output?

console.log(typeof window);

medium

A. "undefined"

B. "object"

C. "function"

D. "null"

Solution

1. Step 1: Understand the 'window' object context

   The 'window' object exists in browsers as the global object for the page.

2. Step 2: Check Node.js global objects

   Node.js does not have a 'window' object, so it is undefined.

3. Final Answer:

   "undefined" -> Option A

4. Quick Check:

   window in Node.js = undefined [OK]

Hint: window is browser-only; Node.js has no window [OK]

Common Mistakes:

• Assuming window exists in Node.js
• Confusing global and window objects
• Expecting 'object' type for window in Node.js

4. Identify the error in this Node.js code snippet:

import fs from 'fs';
const data = fs.readFileSync('file.txt', 'utf8');
console.log(data);

medium

A. The file path must be absolute, not relative.

B. readFileSync requires a callback function.

C. Using import without enabling ES modules causes a syntax error.

D. console.log cannot print file contents.

Solution

1. Step 1: Check import syntax in Node.js

   By default, Node.js uses CommonJS; import requires ES module setup or .mjs extension.

2. Step 2: Validate readFileSync usage

   readFileSync is synchronous and does not need a callback.

3. Final Answer:

   Using import without enabling ES modules causes a syntax error. -> Option C

4. Quick Check:

   import needs ES module setup in Node.js [OK]

Hint: Use require() or enable ES modules for import [OK]

Common Mistakes:

• Thinking readFileSync needs a callback
• Assuming relative paths always cause errors
• Believing console.log can't print strings

5. You want to write a Node.js script that reads a file and sends its content to a web page. Which approach correctly uses Node.js features to do this?

hard

A. Use Node.js to read the file with 'fs', then serve it via an HTTP server module.

B. Use browser JavaScript to read the file directly and send it to the server.

C. Use Node.js to run code inside the browser to access the file system.

D. Use browser JavaScript to create an HTTP server and read files.

Solution

1. Step 1: Understand Node.js capabilities

   Node.js can read files using 'fs' and create servers using 'http' or similar modules.

2. Step 2: Identify correct client-server roles

   Browser JavaScript cannot read files directly from disk or create servers; Node.js handles server tasks.

3. Final Answer:

   Use Node.js to read the file with 'fs', then serve it via an HTTP server module. -> Option A

4. Quick Check:

   Node.js reads files and serves content [OK]

Hint: Node.js handles files and servers; browsers handle UI [OK]

Common Mistakes:

• Expecting browser JS to read local files without user action
• Trying to run server code inside the browser
• Confusing client and server responsibilities