What is Express.js

Express is a fast, assertive, essential and moderate web framework of Node.js. You can assume express as a layer built on the top of the Node.js that helps manage a server and routes. It provides a robust set of features to develop web and mobile applications.

Let's see some of the core features of Express framework:

• It can be used to design single-page, multi-page and hybrid web applications.
• It allows to setup middlewares to respond to HTTP Requests.
• It defines a routing table which is used to perform different actions based on HTTP method and URL.
• It allows to dynamically render HTML Pages based on passing arguments to templates.

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Why use Express

• Ultra fast I/O
• Asynchronous and single threaded
• MVC like structure
• Robust API makes routing easy

How does Express look like

Let's see a basic Express.js app.

File: basic_express.js

1. var express = require('express');  
2. var app = express();  
3. app.get('/', function (req, res) {  
4.   res.send('Welcome to kansiris!');  
5. });  
6. var server = app.listen(8000, function () {  
7.   var host = server.address().address;  
8.   var port = server.address().port;  
9.   console.log('Example app listening at http://%s:%s', host, port);  
10. });  

Output: