Node.js Tutorial for Beginners
Welcome to the Node.js tutorial for beginners! This guide is designed to help you learn Node.js from scratch. We’ll cover the basics, provide coding examples, and include quiz questions to test your understanding. By the end of this tutorial, you’ll be able to build simple server-side applications using Node.js. Let’s get started!
Introduction to Node.js
Node.js is an open-source, cross-platform JavaScript runtime environment that executes JavaScript code outside of a web browser. It’s built on Chrome’s V8 JavaScript engine and allows developers to use JavaScript for server-side scripting.
Why Learn Node.js?
- Unified Language: Use JavaScript on both the front-end and back-end.
- Scalability: Ideal for building scalable network applications.
- Rich Ecosystem: Thousands of packages available through npm.
- Asynchronous and Event-Driven: Efficient handling of multiple connections.
Setting Up Node.js
Download and Install Node.js
- Visit the official Node.js website.
- Download the LTS (Long Term Support) version for your operating system.
- Run the installer and follow the prompts.
Verify Installation
Open your terminal or command prompt and type:
node -v
This should display the installed Node.js version.
Installing a Code Editor
Choose a code editor like Visual Studio Code, Sublime Text, or Atom.
Your First Node.js Program
Let’s create a simple Node.js application.
Hello World Example
- Create a new directory for your project.
- Inside the directory, create a file named app.js.
app.js
console.log(‘Hello, Node.js!’);
- Run the application:
node app.js
Output:
Hello, Node.js!
Quiz Question
Q1: Which command is used to run a Node.js file named app.js?
A. node app.js
B. run app.js
C. execute app.js
D. start app.js
Answer: A. node app.js
Modules in Node.js
Modules are reusable blocks of code whose existence does not accidentally impact other code.
Built-in Modules
Node.js has several built-in modules, such as fs (file system), http, url, etc.
Using the require Function
To include a module, use the require function.
Example:
const os = require(‘os’);
console.log(‘Platform:’, os.platform());
console.log(‘Architecture:’, os.arch());
Output:
Platform: win32
Architecture: x64
Creating Custom Modules
module1.js
function greet(name) {
return `Hello, ${name}!`;
}
module.exports = greet;
app.js
const greet = require(‘./module1’);
console.log(greet(‘Alice’));
Output:
Hello, Alice!
Quiz Question
Q2: How do you export a function from a module in Node.js?
A. export functionName;
B. exports.functionName = functionName;
C. module.exports = functionName;
D. require(‘functionName’);
Answer: C. module.exports = functionName;
File System Module
The fs module allows you to work with the file system on your computer.
Reading Files
Example:
const fs = require(‘fs’);
fs.readFile(‘example.txt’, ‘utf8’, (err, data) => {
if (err) throw err;
console.log(data);
});
Writing Files
fs.writeFile(‘output.txt’, ‘This is some content.’, (err) => {
if (err) throw err;
console.log(‘File has been saved!’);
});
Quiz Question
Q3: Which method is used to read a file asynchronously in Node.js?
A. fs.readFile()
B. fs.readFileSync()
C. fs.openFile()
D. fs.read()
Answer: A. fs.readFile()
Events in Node.js
Node.js is event-driven, meaning it uses events heavily and is asynchronous.
Using the EventEmitter Class
Example:
const EventEmitter = require(‘events’);
const eventEmitter = new EventEmitter();
// Create an event handler
function myEventHandler() {
console.log(‘An event occurred!’);
}
// Assign the event handler to an event
eventEmitter.on(‘myEvent’, myEventHandler);
// Fire the event
eventEmitter.emit(‘myEvent’);
Output:
An event occurred!
Quiz Question
Q4: Which method is used to bind an event handler to an event in Node.js?
A. eventEmitter.emit()
B. eventEmitter.on()
C. eventEmitter.bind()
D. eventEmitter.addEventListener()
Answer: B. eventEmitter.on()
Creating a Web Server
Node.js provides the http module to create web servers.
Simple HTTP Server
Example:
const http = require(‘http’);
const server = http.createServer((req, res) => {
res.statusCode = 200;
res.setHeader(‘Content-Type’, ‘text/plain’);
res.end(‘Hello, World!\n’);
});
const PORT = 3000;
server.listen(PORT, () => {
console.log(`Server running at http://localhost:${PORT}/`);
});
Run the server:
node app.js
Visit http://localhost:3000/ in your browser to see the output.
Quiz Question
Q5: Which module is used to create a web server in Node.js?
A. http
B. web
C. server
D. net
Answer: A. http
npm and Packages
npm (Node Package Manager) is the default package manager for Node.js.
Initializing a Project
npm init -y
This command creates a package.json file.
Installing Packages
npm install express
This installs the express package locally.
Using Installed Packages
Example:
const express = require(‘express’);
const app = express();
app.get(‘/’, (req, res) => {
res.send(‘Hello, Express.js!’);
});
const PORT = 3000;
app.listen(PORT, () => {
console.log(`Server running at http://localhost:${PORT}/`);
});
Quiz Question
Q6: What command is used to install a package using npm?
A. npm get [package-name]
B. npm install [package-name]
C. npm add [package-name]
D. npm new [package-name]
Answer: B. npm install [package-name]
Asynchronous Programming
Node.js uses an asynchronous, non-blocking I/O model.
Callbacks
Functions passed as arguments to other functions.
Example:
function fetchData(callback) {
setTimeout(() => {
callback(‘Data received’);
}, 2000);
}
fetchData((data) => {
console.log(data);
});
Output:
Data received
Promises
An alternative to callbacks for handling asynchronous operations.
Example:
function fetchData() {
return new Promise((resolve) => {
setTimeout(() => {
resolve(‘Data received’);
}, 2000);
});
}
fetchData().then((data) => {
console.log(data);
});
Async/Await
Simplifies working with Promises.
Example:
async function getData() {
const data = await fetchData();
console.log(data);
}
getData();
Quiz Question
Q7: Which of the following is NOT a way to handle asynchronous code in Node.js?
A. Callbacks
B. Promises
C. Async/Await
D. Synchronous loops
Answer: D. Synchronous loops
Building a Simple API with Express.js
Express.js is a minimal and flexible Node.js web application framework.
Setting Up Express.js
Install Express:
npm install express
Create app.js:
const express = require(‘express’);
const app = express();
app.use(express.json());
const PORT = 3000;
app.listen(PORT, () => {
console.log(`Server running at http://localhost:${PORT}/`);
});
Creating Routes
GET Route:
app.get(‘/’, (req, res) => {
res.send(‘Welcome to my API!’);
});
POST Route:
app.post(‘/data’, (req, res) => {
const receivedData = req.body;
res.send(`Data received: ${JSON.stringify(receivedData)}`);
});
Testing the API
Use tools like Postman or curl to test your API endpoints.
Example using curl:
curl -X POST -H “Content-Type: application/json” -d ‘{“name”:”Alice”}’ http://localhost:3000/data
Output:
Data received: {“name”:”Alice”}
Quiz Question
Q8: Which middleware is used in Express.js to parse JSON bodies?
A. express.urlencoded()
B. express.static()
C. express.json()
D. bodyParser.text()
Answer: C. express.json()
Conclusion
Congratulations! You’ve covered the basics of Node.js, including setting up your environment, understanding modules, working with the file system, handling events, creating a web server, using npm, asynchronous programming, and building a simple API with Express.js. Keep practicing and building projects to reinforce your learning.
Final Quiz
Q9: What does the require function do in Node.js?
A. Imports modules
B. Exports modules
C. Reads files
D. Creates servers
Answer: A. Imports modules
Q10: Which of the following is a correct way to start a Node.js application named server.js?
A. start server.js
B. node server.js
C. run server.js
D. execute server.js
Answer: B. node server.js
