How to write code using module.exports in Node.js ?
module is a discrete program, contained in a single file in Node.js. They are tied to files with one module per file. module.exports is an object that the current module returns when it is “required” in another program or module.
We are going to see a simple code like the calculator to learn how to use module.exports in Node.js. I will walk you through step by step.
Step 1: Create two files “app.js” and “calculator.js” in your project folder. And initialize the project through npm in the terminal.
npm init
Step 2: Now we have a nodeJS based project with “app.js” as its entry point. Now let’s first code “calculator.js“. We will create a class named Calculator in it. It would have several member functions namely:
- preIncrement: For the prefix increment operation
- postIncrement: For the postfix increment operation
- preDecrement: For the prefix decrement operation
- postDecrement: For the postfix decrement operation
- add: For addition of two numbers
- subtract: For subtraction of two numbers
- multiply: For multiplication of two numbers
- division: For division of two numbers
And at last, we export the Calculator Class through the module.exports
calculator.js
// ***** calculator.js file ***** class Calculator { // Constructor to create object of the class Calculator() { } // Prefix increment operation preIncrement(a) { return ++a; } // Postfix increment operation postIncrement(a) { return a++; } // Prefix decrement operation preDecrement(a) { return --a; } // Postfix decrement operation postDecrement(a) { return a--; } // Addition of two numbers add(a, b) { return a + b; } // Subtraction of two numbers subtract(a, b) { return a - b; } // Division of two numbers divide(a, b) { return a / b; } // Multiplication of two numbers multiply(a, b){ return a * b; } } // Exporting Calculator as attaching // it to the module object module.exports= Calculator; |
Step 3: Now let’s code the “app.js” file.
First, we will import the Calculator class by requiring it from the “calculator.js” file. Then we create an object “calc” of Calculator class to use its member methods.
app.js
// ***** app.js file ****** // Importing Calculator class const Calculator = require( './calculator.js' ); // Creating object of calculator class const calc = new Calculator(); /* Using all the member methods defined in Calculator */ console.log(calc.preIncrement(5)) console.log(calc.postIncrement(5)) console.log(calc.preDecrement(6)) console.log(calc.postDecrement(6)) console.log(calc.add(5, 6)) console.log(calc.subtract(5, 6)) console.log(calc.divide(5, 6)) console.log(calc.multiply(5, 6)) |
Step to run the application: Open the terminal and type the following command.
node app.js
In this way, you can use module.exports in node.js. In place of class here you can pass any variable, literal, function, or object. And later import it by using require()
Contact Us