The Essential Node.js Guide for Developers

The organized summary will now include more details and code examples for each section.

Essential Node.js Guide for Developers

1. Introduction to Node.js

• What is Node.js?
  • Definition: Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine.
  • Usage: Designed for building scalable network applications.
  • Architecture: Non-blocking, event-driven architecture makes it efficient and suitable for data-intensive real-time applications.

2. Setting Up Node.js

• Installation
  • Using Official Website: Download the installer from nodejs.org and follow the installation steps.
  • Using nvm (Node Version Manager):

    # Install nvm
    curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.38.0/install.sh | bash
    # Install Node.js
    nvm install node
    # Verify Installation
    node -v
    npm -v

3. Core Concepts

• Modules
  • Built-in Modules: Examples include fs for file system operations, http for creating servers.
  • const fs = require('fs'); fs.readFile('file.txt', 'utf8', (err, data) => { if (err) throw err; console.log(data); });
  • Creating and Importing Custom Modules:
  • // math.js exports.add = (a, b) => a + b; // app.js const math = require('./math'); console.log(math.add(2, 3)); // 5
• Event Loop
  • Definition: Handles all asynchronous callbacks.
  • Example:

    setTimeout(() => {
      console.log('This will run after 1 second');
    }, 1000);

• NPM (Node Package Manager)
  • Installing Packages:

    npm install express

  • Managing Dependencies with package.json:

    {
      "name": "my-app",
      "version": "1.0.0",
      "dependencies": {
        "express": "^4.17.1"
      }
    }

4. Building a Simple Server

• HTTP Module
  • Creating a Basic Server:

    const http = require('http');
    const server = http.createServer((req, res) => {
      res.statusCode = 200;
      res.setHeader('Content-Type', 'text/plain');
      res.end('Hello, World!\n');
    });
    server.listen(3000, '127.0.0.1', () => {
      console.log('Server running at http://127.0.0.1:3000/');
    });

5. Working with Express

• Introduction to Express.js
  • Definition: Minimalist web framework for Node.js.
  • Features: Simplifies route handling and middleware integration.
• Setting Up Express
  • Installation:

    npm install express

• Creating an Express App
  • Basic Setup:
  • const express = require('express'); const app = express(); const port = 3000; app.get('/', (req, res) => { res.send('Hello, World!'); }); app.listen(port, () => { console.log(`Server running at http://localhost:${port}/`); });

6. Middleware and Routing

• Middleware Functions
  • Definition: Functions executed during the lifecycle of a request to the server.
  • Usage:

    app.use((req, res, next) => {
      console.log('Request URL:', req.originalUrl);
      next();
    });

• Routing
  • Defining Routes:

    app.get('/users', (req, res) => {
      res.send('User List');
    });
    app.post('/users', (req, res) => {
      res.send('Add User');
    });

7. Error Handling

• Handling Errors in Express
  • Using Middleware:

    app.use((err, req, res, next) => {
      console.error(err.stack);
      res.status(500).send('Something broke!');
    });

8. Connecting to Databases

• MongoDB with Mongoose
  • Setting Up:
  • const mongoose = require('mongoose'); mongoose.connect('mongodb://localhost:27017/mydatabase', { useNewUrlParser: true, useUnifiedTopology: true }) .then(() => console.log('MongoDB connected')) .catch(err => console.log(err)); const userSchema = new mongoose.Schema({ name: String }); const User = mongoose.model('User', userSchema); const newUser = new User({ name: 'Alice' }); newUser.save().then(() => console.log('User saved'));

9. Real-time Communication

• Socket.IO
  • Basic Usage:
  • const http = require('http'); const socketIo = require('socket.io'); const server = http.createServer((req, res) => { res.writeHead(200); res.end('Hello, World!'); }); const io = socketIo(server); io.on('connection', (socket) => { console.log('a user connected'); socket.on('disconnect', () => { console.log('user disconnected'); }); }); server.listen(3000, () => { console.log('Server running at http://localhost:3000/'); });

10. Testing and Debugging

• Using Mocha and Chai for Testing
  • Installation:
  • npm install mocha chai --save-dev
  • Example Test:
  • const assert = require('chai').assert; describe('Array', function() { it('should return -1 when value is not present', function() { assert.equal([1, 2, 3].indexOf(4), -1); }); });
• Debugging with Node.js
  • Using Built-in Debugger:

    node inspect server.js

  • Using nodemon for Auto-restart:

    npm install -g nodemon
    nodemon server.js

Reference

For a more detailed guide, please visit the original article on The Essential Node.js Guide for Developers.