NodeJs Tutorial

Node.js Tutorial: Getting Started with Server-Side JavaScript

Node.js is a powerful platform built on Chrome's V8 JavaScript engine, allowing you to execute JavaScript on the server. It is designed to build scalable, fast, and efficient web applications, handling multiple requests simultaneously without blocking the main thread. This tutorial will guide you through the fundamentals of Node.js, from installation to creating a simple server.

1. Installing Node.js and NPM

To get started, you’ll need to install Node.js on your machine. Node.js comes with NPM (Node Package Manager), which helps you manage packages and libraries for your projects.

Steps:

Windows / macOS / Linux:
- Visit the Node.js website and download the latest stable version.
- Run the installer and follow the instructions.
- To verify the installation, open a terminal or command prompt and run the following commands:
  bash
  node -v npm -v
- You should see the version numbers of both Node.js and NPM.

2. Creating Your First Node.js Application

Let’s start by creating a simple Node.js application that sets up a basic HTTP server and responds with "Hello, World!".

Steps:

Create a new directory for your project:

bash

mkdir my-first-node-app
cd my-first-node-app

Initialize a Node.js project:
bash
npm init -y
This command generates a package.json file, which contains information about your project and its dependencies.
Create a new file named app.js in your project folder.

Write the following code inside app.js to create an HTTP server:

// Import the HTTP module
const http = require('http');

// Create a server object
const server = http.createServer((req, res) => {
    res.writeHead(200, { 'Content-Type': 'text/html' });
    res.write('Hello, World!');
    res.end();
});

// The server listens on port 3000
server.listen(3000, () => {
    console.log('Server running on http://localhost:3000');
});

To run the server, use the following command:
bash
node app.js
Open your browser and navigate to http://localhost:3000. You should see the message "Hello, World!".

3. Understanding Modules and NPM

Node.js has a modular architecture, and you can import different modules (either built-in or third-party) to extend its functionality.

Built-In Modules:

fs: File system operations
http: Create HTTP servers
path: Handle file paths
os: Get information about the operating system

Here’s an example of reading a file with the fs module:

const fs = require('fs');

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

Using NPM Packages:

You can install third-party modules using NPM. For example, to install the popular express framework, you can run:

npm install express

Here’s how to create a basic Express app:

const express = require('express');
const app = express();

// Define a route
app.get('/', (req, res) => {
    res.send('Hello from Express!');
});

// Start the server
app.listen(3000, () => {
    console.log('Express server running on http://localhost:3000');
});

5. Working with the File System

Node.js allows you to interact with the file system to read, write, or delete files using the built-in fs module.

Reading a File:

javascript

const fs = require('fs');

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

Writing to a File:

javascript

const fs = require('fs');

fs.writeFile('output.txt', 'Hello, Node.js!', (err) => {
    if (err) throw err;
    console.log('File has been saved!');
});

6. Node.js with Databases

Node.js can interact with various databases like MySQL, MongoDB, or PostgreSQL. Let’s look at an example using MongoDB with the mongoose package.

Steps:

Install mongoose:
bash
npm install mongoose
Connect to a MongoDB database:

javascript

const mongoose = require('mongoose');

mongoose.connect('mongodb://localhost:27017/mydatabase', { useNewUrlParser: true, useUnifiedTopology: true });

const db = mongoose.connection;
db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', () => {
    console.log('Connected to MongoDB');
});

Define a schema and a model:

javascript

const userSchema = new mongoose.Schema({
    name: String,
    age: Number
});

const User = mongoose.model('User', userSchema);

// Create a new user
const user = new User({ name: 'John', age: 30 });
user.save().then(() => console.log('User saved!'));

7. Conclusion

Node.js is an incredibly powerful tool for building fast and scalable web applications. It allows you to use JavaScript on the server-side, making full-stack development more streamlined. With an active ecosystem and vast library of modules, Node.js is an excellent choice for developing everything from RESTful APIs to real-time applications like chat apps.

As you continue learning Node.js, explore more advanced topics such as: