How to Create Modules in Node.js ?

Modules are the collection of JavaScript codes in a separate logical file that can be used in external applications on the basis of their related functionality. Modules are popular as they are easy to use and reusable. To create a module in Node.js, you will need the exports keyword. This keyword tells Node.js that the function can be used outside the module.

Syntax:

exports.function_name = function(arg1, arg2, ....argN) {
    // function body
};  

Example of a custom node module:

Create a file that you want to export

javascript

// File name: calc.js

exports.add = function (x, y) {
    return x + y;
};

exports.sub = function (x, y) {
    return x - y;
};

exports.mult = function (x, y) {
    return x * y;
};

exports.div = function (x, y) {
    return x / y;
};

Use the ‘require’ keyword to import the file

javascript

// File name: App.js
const calculator = require('./calc');

let x = 50, y = 20;

console.log("Addition of 50 and 20 is "
    + calculator.add(x, y));

console.log("Subtraction of 50 and 20 is "
    + calculator.sub(x, y));

console.log("Multiplication of 50 and 20 is "
    + calculator.mult(x, y));

console.log("Division of 50 and 20 is "
    + calculator.div(x, y));

Output:

Addition of 50 and 20 is 70
Subtraction of 50 and 20 is 30
Multiplication of 50 and 20 is 1000
Division of 50 and 20 is 2.5