Express – Node.js web application framework – Get started

In this lesson, we will study how to install Express web application framework on Node.js and study the basic routing

How to install the Express

npm install express --save

You can have the following code in server.js

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


app.get('/', (request, response) => {  
  response.send('Hello from Express!')
})

app.listen(port, function () {
  console.log('Example app listening on port 3000!')
})

Now you can start the server

node server.js

Now you can test url http://localhost:3000 in your browser

Really simple to install and run your first piece of code

 
Routing made easy with Express
By default, Express gives you the routing functionality

This is a very basic router example for a home page. It responds with a “Hello World” message

app.get('/', function (req, res) {
  res.send('Hello World!')
})

This is a router with respond to POST request

app.post('/', function (req, res) {
  res.send('Got a POST request')
})

This is a simple example for form submission, see how routes are working here we have GET and POST here with http://localhost:3000/user

app.post('/user', function (req, res) {
	let body=''
	request.on('data',function(data) {
		body += data;
	});
	request.on('end',function(){
		response.writeHead(200, {'Content-Type': 'text/plain'});
		response.end('Posted Value is :'+body);
	});
})

app.get('/user', function (req, res) {
  	var form ="<form method='post'>"
		form+="<div><label>Product Name </label>"
		form+="<input type='text' name='key' /></div>"
		form+="<input type='submit' value='Submit' />"
		form+="</form>"
		res.writeHeader(200, {"Content-Type": "text/html"}); 
		res.end(form)
})

You can define router for named URL segment like this

app.get('/user/:id', function(req, res) {
    res.send('user ' + req.params.id);
});