Requesting in HTTP vs Requesting KoaJS
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.
http Module
Import http module: Import http module and store returned HTTP instance into a variable.
Syntax:
var http = require("http");
Creating and Binding Server: Create a server instance using createServer() method and bind it to some port using listen() method.
Syntax:
const server = http.createServer().listen(port)
Parameter: This method (listen()) accepts a single parameter as mentioned above and described below:
-
port <Number>: Ports are in the range 1024 to 65535 containing both registered and Dynamic ports.
Below example illustrate the use of http module in Node.js.
Example 1: Filename: index.js
// Node.js program to create // http server // Using require to access http module const http = require( "http" ); // Port number const PORT = process.env.PORT || 2020; // Creating server const server = http.createServer( // Server listening on port 2020 function (req, res) { // Write a response to the client res.write( 'Hello w3wiki!' ); res.end(); } ) .listen(PORT, error => { // Prints in console console.log(`Server listening on port ${PORT}`) }); |
Run index.js file using the following command:
node index.js
Output:
Server listening on port 2020
Now type http://127.0.0.1:2020/ OR http://localhost:2020 in a web browser to see the output.
Koa Module
In order to use the Koa module, we need to install the NPM (Node Package Manager) and the following modules (on cmd).
>> npm init // Creates package.json file >> npm install koa --save // Installs express module >> 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
// Node.js program to create server // with help of Koa module // Importing koa 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 w3wiki!" ; }); // 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.
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