ExpressJS – Web framework for Node.js

• Web Applications -Express is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications.
• APIs – With a myriad of HTTP utility methods and middleware at your disposal, creating a robust API is quick and easy.
• Performance – Express provides a thin layer of fundamental web application features, without obscuring Node.js features that you know and love.
• Frameworks – Many popular frameworks are based on Express.

Installing

Assuming you’ve already installed Node.js, create a directory to hold your application, and make that your working directory.

$ mkdir myapp
$ cd myapp

Use the npm init command to create a package.json file for your application. For more information on how package.json works, see Specifics of npm’s package.json handling.

$ npm init

This command prompts you for a number of things, such as the name and version of your application. For now, you can simply hit RETURN to accept the defaults for most of them, with the following exception:

entry point: (index.js)

Enter app.js, or whatever you want the name of the main file to be. If you want it to be index.js, hit RETURN to accept the suggested default file name.

Now install Express in the myapp directory and save it in the dependencies list. For example:

$ npm install express --save

To install Express temporarily and not add it to the dependencies list:

$ npm install express --no-save

Hello world example

First create a directory named myapp, change to it and run npm init. Then install express as a dependency, as per the installation guide.

In the myapp directory, create a file named app.js and copy in the code from the example given below.

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

app.get('/', (req, res) => res.send('Hello World!'))

app.listen(port, () => console.log(`Example app listening on port ${port}!`))