Node.js – Express Framework

How it works!

• Express Overview
• Installing Express
• Hello world Example

Express Overview

Express is a minimal and flexible Node.js web application framework that provides a robust set of features to develop web and mobile applications. It facilitates the rapid development of Node based Web applications. Following are some of the core features of Express framework:

• Allows to set up middlewares to respond to HTTP Requests.
• Defines a routing table that is used to perform different actions based on HTTP Method and URL.
• Allows to dynamically render HTML Pages based on passing arguments to templates.

Installing Express

Firstly, install the Express framework globally using NPM so that it can be used to create a web application using node terminal.

$ npm install express --save

The above command saves the installation locally in the node_modules directory and creates a directory express inside node_modules. You should install the following important modules along with express. body-parser − This is a node.js middleware for handling JSON, Raw, Text and URL encoded form data. cookie-parser − Parse Cookie header and populate req.cookies with an object keyed by the cookie names. multer − This is a node.js middleware for handling multipart/form-data.

$ npm install body-parser --save
$ npm install cookie-parser --save
$ npm install multer --save

Hello world Example

Following is a very basic Express app which starts a server and listens on port 8081 for connection. This app responds with Hello World! for requests to the homepage. For every other path, it will respond with a 404 Not Found.

var express = require('express');
var app = express();
app.get('/', function (req, res) {
   res.send('Hello World');
})
var server = app.listen(8081, function () {
   var host = server.address().address
   var port = server.address().port
   console.log("Example app listening at http://%s:%s", host, port)
})

Save the above code in a file named server.js and run it with the following command

$ node server.js