Modules in Node.js

Create, Publish, Extend & Manage

A module in Node.js is a logical encapsulation of code in a single unit. It is a good practice to always segregate code in such a way that it simplify creating manageable and maintainable for future purposes. Because of this we are creating module in nodejs

Since each module is an independent entity with its own encapsulated functionality, it can be managed as a separate unit of work.

What are modules in Node.js?

There are many modules available in nodejs

• Express framework – Express is a minimal and flexible Node js web application framework that provides a robust set of features for the web and Mobile applications.

• Socket.io – Socket.IO enables real-time bidirectional event-based communication. This module is good for creation of chatting based applications.

• Jade – Jade is a high-performance template engine and implemented with JavaScript for node and browsers.

• MongoDB – The MongoDB Node.js driver is the officially supported node.js driver for MongoDB.

• Restify – restify is a lightweight framework, similar to express for building REST APIs

Creating Module

We can create custom module and include in Nodejs application, Nodejs support this feature.

In the below example we can create our own module and include it in our application

Step 1) Create a file called “add.js” and include the below code.

app.js

//1.Define a Module
    var myExports = module.exports = {};
    
    //2.Create a function in our Module
    myExports.AddNum = function(a, b) {
    
        //3. Returning a value back to the calling function
        return a + b;
    }

We have created our custom module, next we will call this moudle

main.js

// Using require to Include the Addition Module
var Addition = require('./app'); 
// calling the AddNum function in our module
console.log(Addition.AddNum(1, 2)); 

We are using the “require” keyword to include the functionality in the app.js file.

Since the functions in the app.js file are now accessible, we can now make a call to the addition function.

Now run the node command to execute the code “node main.js”

Output

node main.js
3

Click to download

Example for Module,Exports,Require

one.js
------
var one = function() {
    console.log('I am from one');
}

module.exports = one;

two.js
-------
var two = function() {
    console.log('i am from two');
}

module.exports = two;

index.js
--------
var one = require('./one');
var two = require('./two');

module.exports = {
    one: one,
    tow: two
}

app.js
------
var both = require('./converter');
both.one();
both.tow(); 

Output :

I am from one
        i am from two

Different Ways To Use module.exports

1.
    details.js
    ----------
    //exports is an javascript object , we can asign anything
    module.exports = "Hello";
    
    main.js
    --------
    var details = require('./details');
    console.log(details);

    //OutPut
    Hello

    2.
    details.js
    -----------
    var name = 'John';

    var getName = () => name;

    module.exports = getName; // Passing Refrenence

    main.js
    --------
    var details = require('./details');
    console.log(details()); // Call the function

    //OutPut
    John

    3. Best Way exporting 
    details.js
    ----------
    var name = 'John';
    var city = 'Mumbai';

    var getName = () => name;
    var getCity = () => city;

    // Export JSON Object, here we add the logics before we export
    module.exports = {
        getName,
        getCity
    };

    main.js
    --------
    var details = require('./details');
    console.log(details.getName());
    console.log(details.getCity());

    //OutPut
    John
    Mumbai

    4.
    //The above main program can be written as below
    var { getName, getCity } = require('./details');
    console.log(getName());
    console.log(getCity());

    //OutPut
    John
    Mumbai

    5.
    //Directly Export function
    details.js
    -----------
    var name = 'John';
    var city = 'Delhi';
    // Export Functions
    module.exports.getName = () => name;

    //We can attach any number of functitons
    module.exports.getCity = () => city;

    main.js
    -------
    var details = require('./details');
    console.log(details.getName());
    console.log(details.getCity());

    //OutPut
    John
    Delhi

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