Express.js

01. Getting start

## ------------------| One Rule to Rule Them All
npx express-generator -f --git 

## ------------------| Create package.json
npm init -f

## ------------------| Install dependencies 
### Install app directory and save it in the dependencies list
npm install express cors nodemon dotenv
### Install temporarily and not add it to the dependencies list
npm install express cors nodemon dotenv --no-save

## ------------------| Changes on package.json
"scripts": {
  "start": "nodemon src/app.js"
}

## ------------------| Create .gitignore file
/node_modules
.env
/.pnp
.pnp.js
/coverage
/build
.DS_Store
.env.local
.env.development.local
.env.test.local
.env.production.local
npm-debug.log*
yarn-debug.log*
yarn-error.log* 

• app.js

const express = require('express')
const cors = require('cors') 
const app = express()
const port = 3000

// Loads environment variables from a .env file [to use process.env.NAME]
require('dotenv').config()

// Middlewares [app.use(<a function>);]
app.use(cors());

// Register Routes
app.get('/api/v1/test', (req, res) => {
    res.send('Hello h4rithd.com')
})

app.listen(port, () => {
    console.log(`App listening on port ${port}`)
})

02. Register Routes

## ------------------| For GET Request 
### [text/html]
app.get('/api/v1/test', (req, res) => {
    res.send('Hello h4rithd.com')
})
### [application/json]
app.get('/api/v1/json', (req, res) => {
    res.json({
        message: "Hello h4rithd.com"
    })
})

## ------------------| For POST Request
app.post('/api/v1/test', (req, res) => {
    res.send('Hello h4rithd.com')
})

## ------------------| For PUT Request
app.put('/api/v1/test', (req, res) => {
    res.send('Hello h4rithd.com')
})

## ------------------| For POST Request
app.post('/api/v1/test', (req, res) => {
    res.send('Hello h4rithd.com')
})

03. Database Management

03.1 MongoDB

• Getting started

## ------------------| Install dependencies
npm init -y
npm install mongoose express nodemon

• Connect to database

const mongoose = require('mongoose');
mongoose.connect('mongodb//<username>:<password>@localhost/my_database').then(() => {
    app.listen(port, () => {
        console.log(`App listening on port ${port}`)
    })
});

• Insert data to database [Basic]

const mongoose = require('mongoose');
const Schema = mongoose.Schema;

const Item = new Schema({
    item: String,
});

mongoose.model("Item", Item);

app.post('/items', async (req, res) => {
    const item = req.body;
    const ItemModel = mongoose.model("Item");
    const myItem = new ItemModel(item);
    const createdItem = await myItem.save(); // Save data to database
    console.log(createdItem);
    res.send('Hello h4rithd.com');
})

• Insert data to database [Structured]

## ------------------| src/app.js
const mongoose = require('mongoose');
const express = require('express')
const cors = require('cors')
const app = express()
const port = 3000

require('./models/item');

app.use(cors());
app.use(express.json())

app.post('/items', require("./route/insertItem"));

mongoose.connect('mongodb//<username>:<password>@localhost/my_database').then(() => {
    app.listen(port, () => {
        console.log(`App listening on port ${port}`)
    })
});

## ------------------| ./src/models/item.js
const mongoose = require('mongoose');
const Schema = mongoose.Schema;

const Item = new Schema({
    item: {
        type: String,
        require: true
    },
});

mongoose.model("Item", Item);

## ------------------| ./route/insertItem.js
const mongoose = require('mongoose');

module.exports = async (req, res) => {
    const item = req.body;
    const ItemModel = mongoose.model("Item");
    const myItem = new ItemModel(item);
    const createdItem = await myItem.save(); // Save data to database
    console.log(createdItem);
    res.send('Hello h4rithd.com');
};

03.2 SQLiteDB

• Getting started

npm init -y
npm install express sqlite3 body-parser bcryptjs jsonwebtoken nodemon

## ------------------| Changes on package.json
"scripts": {
  "start": "nodemon src/app.js"
}

• Create app.js

const express = require('express');
const sqlite3 = require('sqlite3').verbose();
const bodyParser = require('body-parser');
const bcrypt = require('bcryptjs');
const jwt = require('jsonwebtoken');

const app = express();
app.use(bodyParser.json());

const db = new sqlite3.Database('./database.db');

// Create tables if they don't exist
db.serialize(() => {
  db.run(`CREATE TABLE IF NOT EXISTS users (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    username TEXT UNIQUE,
    email TEXT,
    password TEXT,
    name TEXT,
    isAdmin INTEGER
  )`);

  db.run(`CREATE TABLE IF NOT EXISTS messages (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    username TEXT,
    message TEXT,
    date TEXT
  )`);
});

// JWT Secret
const JWT_SECRET = "your_secret_key";

// Register route
app.post('/api/v1/register', (req, res) => {
  const { username, email, password, name, isAdmin } = req.body;

  // Hash password
  const hashedPassword = bcrypt.hashSync(password, 10);

  db.run(`INSERT INTO users (username, email, password, name, isAdmin) VALUES (?, ?, ?, ?, ?)`,
    [username, email, hashedPassword, name, isAdmin ? 1 : 0],
    function (err) {
      if (err) {
        return res.status(400).json({ error: err.message });
      }
      res.json({ message: "User registered successfully" });
    }
  );
});

// Login route
app.post('/api/v1/login', (req, res) => {
  const { username, password } = req.body;

  db.get(`SELECT * FROM users WHERE username = ?`, [username], (err, user) => {
    if (err) return res.status(500).json({ error: err.message });
    if (!user) return res.status(400).json({ error: "User not found" });

    // Compare password
    if (!bcrypt.compareSync(password, user.password)) {
      return res.status(400).json({ error: "Invalid password" });
    }

    // Generate JWT token
    const token = jwt.sign({ id: user.id, username: user.username, isAdmin: user.isAdmin }, JWT_SECRET);
    res.json({ token });
  });
});

// Middleware to authenticate JWT token
const authenticateJWT = (req, res, next) => {
  const token = req.headers.authorization;

  if (!token) return res.status(403).json({ error: "Token missing" });

  jwt.verify(token, JWT_SECRET, (err, user) => {
    if (err) return res.status(403).json({ error: "Invalid token" });
    req.user = user;
    next();
  });
};

// Send message route
app.post('/api/v1/sendMessage', authenticateJWT, (req, res) => {
  const { message } = req.body;
  const username = req.user.username;
  const date = new Date().toISOString();

  db.run(`INSERT INTO messages (username, message, date) VALUES (?, ?, ?)`,
    [username, message, date],
    function (err) {
      if (err) return res.status(500).json({ error: err.message });
      res.json({ message: "Message sent successfully" });
    }
  );
});

// Update user route (Admin only)
app.put('/api/v1/updateUser', authenticateJWT, (req, res) => {
  if (!req.user.isAdmin) return res.status(403).json({ error: "Only admin can update user" });

  const { id, username, email, name, isAdmin } = req.body;
  db.run(`UPDATE users SET username = ?, email = ?, name = ?, isAdmin = ? WHERE id = ?`,
    [username, email, name, isAdmin ? 1 : 0, id],
    function (err) {
      if (err) return res.status(500).json({ error: err.message });
      if (this.changes === 0) return res.status(400).json({ error: "User not found" });
      res.json({ message: "User updated successfully" });
    }
  );
});

// Start server
const PORT = process.env.PORT || 3000;
app.listen(PORT, () => {
  console.log(`Server running on port ${PORT}`);
});

04. Deploying

• Process Manager (PM2)

npm install -g pm2
pm2 start app.js --name "myapp"  --watch
pm2 save           ## save the configuration for restart persistence
pm2 startup        ## set up PM2 to start on boot
pm2 list           ## list all 
pm2 logs "myapp"   ## display logs
pm2 restart        ## restart

• For DEV env

## ------------------| Specify which files or directories to watch (pm2.config.js)
module.exports = {
  apps: [
    {
      name: 'app',
      script: './app.js',
      watch: true,
      ignore_watch: ['node_modules', 'logs']
    }
  ]
};

## pm2 start pm2.config.js

• For PROD env

## ------------------| Set environment variables (pm2.config.js)
module.exports = {
  apps: [
    {
      name: 'app',
      script: './app.js',
      env: {
        NODE_ENV: 'development',
        PORT: 3000
      },
      env_production: {
        NODE_ENV: 'production',
        PORT: 80
      }
    }
  ]
};

## pm2 start pm2.config.js --env production
## pm2 startup