Create custom modules in Node.js

node.js module is a package that contains certain functions or methods for use by those who import them. There are several modules available on the web for developers to use, such as fs, fs-extra, crypto, stream, etc. You can also make your own package and use it in your code.

Syntax

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

Example - Custom Node Module

Create two files named calc.js and index.js and copy the following code snippets.

calc.js is the module where the custom node will hold the node functionality.

index.js will import calc.js and use it in the node process.

calc.js

//Creating a custom node module
// And making different functions
exports.add = function (a, b) {
   return a + b; // Adding the numbers
};

exports.sub = function (a, b) {
   return a - b; // Subtracting the numbers
};

exports.mul = function (a, b) {
   return a * b; // Multiplying the numbers
};

exports.div = function (a, b) {
   return a / b; // Dividing the numbers
};

index.js

// Importing the custom node module with the below statement
var calculator = require('./calc');

var a = 21 , b = 67

console.log("Addition of " + a + " and " + b + " is " + calculator.add(a, b));

console.log("Subtraction of " + a + " and " + b + " is " + calculator.sub(a, b));

console.log("Multiplication of " + a + " and " + b + " is " + calculator.mul(a, b));

console.log("Division of " + a + " and " + b + " is " + calculator.div(a, b));

Output

C:\homeode>> node index.js
Addition of 21 and 67 is 88
Subtraction of 21 and 67 is -46
Multiplication of 21 and 67 is 1407
Division of 21 and 67 is 0.31343283582089554

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