express

1. Routing

2. mkdir my-express-app
cd my-express-app
npm init
npm install express --save

3. The following code is an example of a very basic
route.
const express = require('express')
const app = express()
// respond with "hello world"
when a GET request is made to the
homepage
app.get('/', (req, res) => {
res.send('hello world')
})
const express = require('express');
const app = express();
app.use((req, res) => {
res.send('<h1>Hello, World!</h1>');
});
app.get(‘/’,(req, res) => {
res.send('<h1>Hello, World!</h1>');
});
app.get(‘/use’,(req, res) => {
res.send('<h1>Hello, About US!</h1>');
});
app.listen(8000, () => console.log('Server listening on
port 8000'));

4. The following code is an example of a very basic
route.
const express = require('express')
const app = express()
// respond with "hello world"
when a GET request is made to the
homepage
app.get('/', (req, res) => {
res.send('hello world')
})
const express = require('express');
const app = express();
app.use((req, res) => {
res.send('<h1>Hello, World!</h1>');
});
app.get(‘/’,(req, res) => {
res.send('<h1>Hello, World!</h1>');
});
app.get(‘/use’,(req, res) => {
res.send('<h1>Hello, World!</h1>');
});
app.listen(8000, () => console.log('Server listening on
port 8000'));

5.  npm install -g nodemon
 npm install --save-dev nodemon
 nodemon app.js

6. // Importing the module
const express=require("express")
// Creating express Router
const router=express.Router()
// Handling login request
router.get("/login",(req,res,next)=>{
res.send("This is the login request")
})
module.exports=router
// Importing express module
const express=require("express")
const router=express.Router()
// Handling request using router
router.get("/home",(req,res,next)=>{
res.send("This is the homepage request")
})
// Exporting the router
module.exports=router

7. const express=require("express")
// Importing all the routes
const homeroute=require("./routes/Home.js")
const loginroute=require("./routes/login.js")
// Creating express server
const app=express()
// Handling routes request
app.use("/",homeroute)
app.use("/",loginroute)
app.listen((3000),()=>{
console.log("Server is Running")
})

8. const express = require("express");
const app = express();
app.get("/", function(req, res) {
res.send("This is a get request!!n");
});
app.post("/", function(req, res) {
res.send("This is a post request!!n");
});
app.put("/", function(req, res) {
res.send("This is a put request!!n");
});
app.get("/hey", function(req, res) {
res.send("This is a get request to '/hey'!!n");
});
app.listen(3000);

9. const express = require('express');
const app = express();
// Define a route with a route parameter
app.get('/users/:userId', (req, res) => {
// Access the route parameter value
const userId = req.params.userId;
res.send(`User ID: ${userId}`);
});
// Start the server
app.listen(3000, () => {
console.log('The server is running on port: 3000');
});

10. const express = require('express');
const app = express();
// Custom middleware to log requests
function logRequests(req, res, next) {
console.log(`${req.method} request to ${req.url} at $
{new Date().toLocaleTimeString()}`);
next(); // Proceed to the next middleware or route
}
app.use(logRequests); // Apply it globally
app.get('/', (req, res) => {
res.send('Home Page');
});
app.get('/about', (req, res) => {
res.send('About Page');
});
app.listen(3000, () => {
console.log('Server running on port 3000');
});

11. MULTIPLE MIDDLE
function first(req, res, next) {
console.log('First middleware');
next(); // Move to the next middleware
}
function second(req, res, next) {
console.log('Second middleware');
next(); // Move to the next middleware
}
app.get('/multi', first, second, (req, res) => {
res.send('Multiple middleware executed');
});

12. Cookies

13. var express = require('express’)
var cookieParser = require('cookie-parser’)
var app = express() app.use(cookieParser())
app.get('/', function (req, res)
{ // Cookies that have not been signed
console.log('Cookies: ', req.cookies)
// Cookies that have been signed
console.log('Signed Cookies: ', req.signedCookies) })
app.listen(8080)
// curl command that sends an HTTP request with two cookies
// curl http://127.0.0.1:8080 --cookie "Cho=Kim;Greet=Hello"
https://www.npmjs.com/package/cookie-session

14. Simple view counter example
var cookieSession = require('cookie-session’)
var express = require('express’)
var app = express() app.set('trust proxy', 1)
// trust first proxy
app.use(cookieSession(
{ name: 'session', keys: ['key1', 'key2'] }))
app.get('/', function (req, res, next) {
// Update views
req.session.views = (req.session.views || 0) + 1
// Write response
res.end(req.session.views + ' views') })
app.listen(3000)