Express.js vs KoaJS in Node.js

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:

PORT <Number>: Ports are the endpoints of communication which helps to communicate with the client and the server.
IP <Number>: IPs represent IPv4 or IPv6 address of a host or a device.
Callback <Function>: It accepts a function.

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:

PORT <Number>: Ports are the endpoints of communication which helps to communicate with the client and the server.
IP <Number>: IPs represent IPv4 or IPv6 address of a host or a device.
Callback <Function>: It accepts a function.

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);
});