Express.js vs KoaJS in Node.js (original) (raw)

Last Updated : 14 Sep, 2020

Node.js: Node.js is an open-source and cross-platform runtime environment for executing JavaScript code outside a browser. You need to remember that NodeJS is not a framework and it’s not a programming language. Most of the people are confused and understand it’s a framework or a programming language. We often use Node.js for building back-end services like APIs like Web App or Mobile App.

Express Module: In order to use the express module, we need to install the NPM (Node Package Manager) and the following modules (on cmd).

// Creates package.json file

npm init

// Installs express module

npm install express --save // OR npm i express -s

Import express module: Import express module and store returned instance into a variable.

Syntax:

var express = require("express");

Creating Server: The above syntax calls the "express()" function and creates a new express application which gets stored inside the app variable.

Syntax:

// Importing and creating express application const app = express();
var express = require("express")(); // OR

Sending and listening to the response: It communicates the request and response with the client and the server. It requires PORT <_number_> and IP <_number_> to communicate.

app.listen(PORT, IP, Callback);

Parameter: This method accepts three parameters as mentioned above and described below:

The below example illustrates the Express.js module in Node.js.

Example 1: Filename: index.js

javascript ``

// Node.js program to create server
// with help of Express module

// Importing express
const express = require('express');

// Creating new express app
const app = express();

// PORT configuration const PORT = process.env.PORT || 2020;

// IP configuration const IP = process.env.IP || 2021;

// Create a route for the app app.get('/', (req, res) => { res.send('Hello Vikas_g from geeksforgeeks!'); });

// Create a route for the app app.get('*', (req, res) => { res.send('OOPS!! The link is broken...'); });

// Server listening to requests app.listen(PORT, IP, () => { console.log(The Server is running at: http://localhost:${PORT}/); });

``

Run index.js file using the following command:

node index.js

Output:

The Server is running at: http://localhost:2020

Now type http://127.0.0.1:2020/ OR http://localhost:2020/ in a web browser to see the output.

KoaJS Module: In order to use the KoaJS module, we need to install the NPM (Node Package Manager) and the following modules (on cmd).

// Creates package.json file

npm init

// Installs koa module<

npm install koa --save npm i koa -s // OR

Import KoaJS module: Import KoaJS module and store returned instance into a variable.

Syntax:

var koa = require("koa"); // Importing koa module

Creating Server: The above syntax imports the koa module and creates a new koa application which gets stored inside the app variable.

Syntax:

const app = new koa(); // Creating koa application

Sending and listening to the response: It communicates the request and response with the client and the server. It requires PORT <_number_> and IP <_number_> to communicate.

app.listen(PORT, IP, Callback);

Parameter: This method accepts three parameters as mentioned above and described below:

The below example illustrates the KoaJS module in Node.js.

Example 2: Filename: index.js

javascript `

// Node.js program to create server // with help of Koa module

// Importing koa module const koa = require('koa');

// Creating new koa app const app = new koa();

// PORT configuration const PORT = process.env.PORT || 2020;

// IP configuration const IP = process.env.IP || 2021;

app.use(function *() { this.body = "Hello GeeksForGeeks!"; });

// Server listening to requests app.listen(PORT, IP, ()=>{ console.log("Server started at port", PORT); });

`

Run index.js file using the following command:

node index.js

Output:

The Server is running at port 2020

Now type http://127.0.0.1:2020/ OR http://localhost:2020/ in a web browser to see the output.