npm install express

npm install express --save

const express = require('express');
const app = express();
const port = 8080;

// Define a route for GET requests to the root URL
app.get('/', (req, res) => {
  res.send('Hello World from Express!');
});

// Start the server
app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`);
});

node app.js

const express = require('express');
const app = express();
const port = 8080;

// Respond to GET request on the root route
app.get('/', (req, res) => {
  res.send('GET request to the homepage');
});

// Respond to POST request on the root route
app.post('/', (req, res) => {
  res.send('POST request to the homepage');
});

// Respond to GET request on the /about route
app.get('/about', (req, res) => {
  res.send('About page');
});

// Catch all other routes
app.all('*', (req, res) => {
  res.status(404).send('404 - Page not found');
});

// Start the server
app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`);
});

const express = require('express');
const app = express();
const port = 8080;

// Route with parameters
app.get('/users/:userId/books/:bookId', (req, res) => {
  // Access parameters using req.params
  res.send(`User ID: ${req.params.userId}, Book ID: ${req.params.bookId}`);
});

app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`);
});

const express = require('express');
const app = express();
const port = 8080;

// Route handling query parameters
app.get('/search', (req, res) => {
  // Access query parameters using req.query
  const { q, category } = req.query;
  res.send(`Search query: ${q}, Category: ${category || 'none'}`);
});

app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`);
});

const express = require('express');
const app = express();
const port = 8080;

// Middleware to parse JSON request bodies
app.use(express.json());

// Middleware to parse URL-encoded request bodies
app.use(express.urlencoded({ extended: true }));

// Middleware to serve static files from a directory
app.use(express.static('public'));


// POST route that uses JSON middleware
app.post('/api/users', (req, res) => {
  // req.body contains the parsed JSON data
  console.log(req.body);
  res.status(201).json({ message: 'User created', user: req.body });
});

app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`);
});

const express = require('express');
const app = express();
const port = 8080;

// Route that may throw an error
app.get('/error', (req, res) => {
  // Simulating an error
  throw new Error('Something went wrong!');
});

// Route that uses next(error) for asynchronous code
app.get('/async-error', (req, res, next) => {
  // Simulating an asynchronous operation that fails
  setTimeout(() => {
    try {
      // Something that might fail
      const result = nonExistentFunction(); // This will throw an error
      res.send(result);
    }
    catch (error) {
      next(error); // Pass errors to Express
    }
    }, 100);
});

// Custom error handling middleware
// Must have four parameters to be recognized as an error handler
app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(500).send('Something broke!');
});

app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`);
});

const express = require('express');
const path = require('path');
const app = express();
const port = 8080;

// Serve static files from the 'public' directory
app.use(express.static('public'));

// You can also specify a virtual path prefix
app.use('/static', express.static('public'));

// Using absolute path (recommended)
app.use('/assets', express.static(path.join(__dirname, 'public')));

app.get('/', (req, res) => {
  res.send(`
    
Static Files Example
    
    
    
  `);
});

app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`);
});

const express = require('express');
const router = express.Router();

// Middleware specific to this router
router.use((req, res, next) => {
  console.log('Users Router Time:', Date.now());
  next();
});

// Define routes
router.get('/', (req, res) => {
  res.send('Users home page');
});

router.get('/:id', (req, res) => {
  res.send(`User profile for ID: ${req.params.id}`);
});

module.exports = router;

const express = require('express');
const router = express.Router();

// Define routes
router.get('/', (req, res) => {
  res.send('Products list');
});

router.get('/:id', (req, res) => {
  res.send(`Product details for ID: ${req.params.id}`);
});

module.exports = router;

const express = require('express');
const usersRouter = require('./routes/users');
const productsRouter = require('./routes/products');

const app = express();
const port = 8080;

// Use the routers
app.use('/users', usersRouter);
app.use('/products', productsRouter);

app.get('/', (req, res) => {
  res.send('Main application home page');
});

app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`);
});

const express = require('express');
const app = express();
const port = 8080;

// Set the view engine to EJS
app.set('view engine', 'ejs');

// Set the directory where templates are located
app.set('views', './views');

// Route that renders a template
app.get('/', (req, res) => {
  const data = {
    title: 'Express Template Example',
    message: 'Hello from EJS!',
    items: ['Item 1', 'Item 2', 'Item 3']
  };

  // Renders the views/index.ejs template
  res.render('index', data);
});

app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`);
});

npm install ejs

<!DOCTYPE html>
<html>
<head>
  <title><%= title %></title>
</head>
<body>
  <h1><%= title %></h1>
  <p><%= message %></p>

  <h2>Items:</h2>
  <ul>
    <% items.forEach(function(item) { %>
      <li><%= item %></li>
    < % }); %>
  </ul>
</body>
</html>

# Install the generator globally
npm install -g express-generator

# Create a new Express application
express --view=ejs myapp

# Navigate to the app directory
cd myapp

# Install dependencies
npm install

# Start the app
npm start

myapp/
├── app.js
├── bin/
│  └── www
├── package.json
├── public/
│  ├── images/
│  ├── javascripts/
│  └── stylesheets/
│    └── style.css
├── routes/
│  ├── index.js
│  └── users.js
└── views/
  ├── error.ejs
  └── index.ejs

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

// Security middleware
app.use(helmet());

// CORS configuration
app.use(cors({
  origin: 'https://example.com',
  methods: ['GET', 'POST'],
  allowedHeaders: ['Content-Type', 'Authorization']
}));

// Other middleware and routes
// ...