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

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

This is 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);
});