Node.js: Working With Modules

Modules are generally set of functions that you can include in your application.

These could be built-in functions that are part of the Node.js library or imported from a third-party library.

Built-in Modules

Node.js has a set of built-in modules which you can use without any further installation.

These include:

Module	Description
assert	Provides a set of assertion tests
buffer	To handle binary data
child_process	To run a child process
cluster	To split a single Node process into multiple processes
crypto	To handle OpenSSL cryptographic functions
dgram	Provides implementation of UDP datagram sockets
dns	To do DNS lookups and name resolution functions
domain	Deprecated. To handle unhandled errors
events	To handle events
fs	To handle the file system
http	To make Node.js act as an HTTP server
https	To make Node.js act as an HTTPS server.
net	To create servers and clients
os	Provides information about the operation system
path	To handle file paths
punycode	Deprecated. A character encoding scheme
querystring	To handle URL query strings
readline	To handle readable streams one line at the time
stream	To handle streaming data
string_decoder	To decode buffer objects into strings
timers	To execute a function after a given number of milliseconds
tls	To implement TLS and SSL protocols
tty	Provides classes used by a text terminal
url	To parse URL strings
util	To access utility functions
v8	To access information about V8 (the JavaScript engine)
vm	To compile JavaScript code in a virtual machine
zlib	To compress or decompress files

Using a Module

To use or require a module, we use the require() function followed by the name of the module

Example:

let http = require('http');

Creating Your Own Module

You can create your own modules and include them in your project.

First, let us create a module called Time.js as follows

exports.mytTime = function() {
    return Date();
}

Next, let us create a main.js file where we can use this newly-created module

let http = require("http");
let date = require('./Time');

http.createServer(function (request, response) {
   response.writeHead(200, {'Content-Type': 'text/plain'});
   
   // Send the response body as "Hello World"
   response.end(`Hello world. Thank you The time is ${date.mytTime()}`);
}).listen(80);

Next we run the file on port 80 and we get the response printed on the screen.

This is how we can create modules that we can use in our project