Node JS - Comprehensive Guide

Here's a power-packed roadmap for Node.js, including structured concepts, example code snippets

1. Introduction to Node.js:

• What is Node.js?
• Event-driven, non-blocking I/O model.
• Setting up a Node.js development environment.

2. Understanding Modules:

• CommonJS modules.
• Creating and exporting modules.
• Example: Creating and using a custom module.

// mymodule.js
module.exports = {
  greet: function () {
    return 'Hello, Node.js!';
  },
};        

3. Asynchronous Programming:

• Callbacks and the callback hell problem.
• Promises and async/await.
• Example: Reading a file asynchronously using callbacks.

// Using callbacks
const fs = require('fs');

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

4. Working with the File System:

• Reading and writing files.
• Creating and deleting directories.
• Example: Writing data to a file.

// Writing to a file
const fs = require('fs');

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

5. Node.js and HTTP:

• Building HTTP servers.
• Handling HTTP requests and responses.
• Example: Creating a basic HTTP server.

// Creating an HTTP server
const http = require('http');

const server = http.createServer((req, res) => {
  res.writeHead(200, { 'Content-Type': 'text/plain' });
  res.end('Hello, Node.js!');
});

server.listen(3000, 'localhost', () => {
  console.log('Server is listening on port 3000');
});        

6. Express.js Framework:

• Introduction to Express.js.
• Routing, middleware, and templates.
• Example: Creating a simple Express app.

// Creating an Express app
const express = require('express');
const app = express();

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

app.listen(3000, () => {
  console.log('Express server is listening on port 3000');
});        

7. Databases and MongoDB:

• Connecting to databases.
• CRUD operations with MongoDB.
• Example: Creating a MongoDB connection and performing CRUD operations.

// MongoDB connection and CRUD
const MongoClient = require('mongodb').MongoClient;
const url = 'mongodb://localhost:27017/mydb';

MongoClient.connect(url, (err, db) => {
  if (err) throw err;
  console.log('Database connected.');

  const dbo = db.db('mydb');
  const collection = dbo.collection('mycollection');

  // CRUD operations here
});        

8. Authentication and Authorization:

• Implementing user authentication.
• Role-based access control.
• Example: Setting up user authentication using Passport.js.

// User authentication with Passport.js
const passport = require('passport');
const LocalStrategy = require('passport-local').Strategy;

passport.use(new LocalStrategy(
  function(username, password, done) {
    // Authenticate user here
  }
));        

9. Real-Time Applications with Socket.io:

• Building real-time web applications.
• WebSocket communication.
• Example: Creating a basic chat application using Socket.io.

// Real-time chat with Socket.io
const io = require('socket.io')(http);

io.on('connection', (socket) => {
  console.log('A user connected');
  
  socket.on('chat message', (msg) => {
    io.emit('chat message', msg);
  });
});        

10. Testing and Debugging: - Writing unit tests with frameworks like Mocha and Chai. - Debugging Node.js applications. - Example: Writing a unit test for a Node.js module.

// Unit test with Mocha and Chai
const assert = require('chai').assert;

describe('Math', () => {
  it('should return the sum of two numbers', () => {
    assert.equal(2 + 3, 5);
  });
});        

11. Advanced Topics: - Promises and async/await in-depth. - Building RESTful APIs with Express.js. - GraphQL with Node.js. - Microservices architecture with Node.js. - Scaling Node.js applications.