How to export multiple values or elements in a Module ?

In Node.js, modules are an essential part of the architecture, allowing you to organize code into separate files and reuse it across different parts of your application. One common requirement is to export multiple values or elements from a module so that they can be imported and used in other parts of the application. This article explores different methods for exporting multiple values or elements from a Node.js module, including exporting objects, arrays, and functions.

Introduction to Modules in Node.js

Modules in Node.js are JavaScript files that are encapsulated and can export their functionality to be reused by other files. Node.js uses the CommonJS module system, where each file is treated as a separate module.

Syntax

export let element1
export const someValue
export function foo(){...}

Note: As we are exporting multiple values, while importing those values it is mandatory to use the same name of the corresponding object.

Steps to Setup the Application

Step 1: Initialize the NodeJS application using the following command

npm init

Step 2: express module which is a web framework for NodeJS in your project using the following commands.

npm install express

Project Structure:

Here, In the root folder of "GFG-MODULES" there are 3 files namely "index.html",  "index.js" and our "package.json" file along with these, it has the "modules" folder containing a file named "siteData.js".

Step 3: Configuring package.json file so that it won't cause any errors when export statements are used , Firstly in our package.json file, add the following property:

"type" : "module"

When you have the "type: module" property, then your source code can use the import syntax, otherwise, it will cause errors and will only support the "require" syntax. Your package.json file should look similar to this

{
  "name": "gfg-modules",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "type": "module",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "GFG",
  "license": "ISC"
}

Step 4: Exporting multiple elements from the module.

In siteData.js, we have exported multiple elements from our module "siteName".

// siteData.js

export const siteName = "GeeksForGeeks";
export const url = "https://www.geeksforgeeks.org/";
export const founderName = "Sandeep Jain";
export const aboutSite = "A Computer Science portal for geeks";
export let siteContent =
  "Computer science and Programming articles along with Courses";

Step 5: Importing the multiple elements in index.js

// index.js

import {
  siteName,
  url,
  founderName,
  aboutSite,
  siteContent,
} from "./modules/siteData.js";

console.log("Site Data is as follows:");
console.log(`Site name: \t${siteName}`);
console.log(`Site url : \t${url}`);
console.log(`Founder name: \t${founderName}`);
console.log(`About site: \t${aboutSite}`);
console.log(`Site Content: \t${siteContent}`);

Here, as we have exported multiple values, hence our export type was "Named Exports" and due to it, we have imported all the values by the same corresponding names.

Step to Run Application: Run the application using the following command from the root directory of the project

node index.js

Output:

Site Data is as follows:
Site name:      GeeksForGeeks
Site url :      https://www.geeksforgeeks.org/
Founder name:   Sandeep Jain
About site:     A Computer Science portal for geeks
Site Content:   Computer science and Programming articles along with Courses

Exporting an Object

The most common method to export multiple values is to package them into an object. This allows you to group related values together and export them as a single entity.

// math.js
const add = (a, b) => a + b;
const subtract = (a, b) => a - b;
const multiply = (a, b) => a * b;
const divide = (a, b) => a / b;

module.exports = {
    add,
    subtract,
    multiply,
    divide
};

You can then import this object and use its properties:

// app.js
const math = require('./math');

console.log(math.add(5, 3));       // Outputs: 8
console.log(math.subtract(5, 3));  // Outputs: 2
console.log(math.multiply(5, 3));  // Outputs: 15
console.log(math.divide(6, 3));    // Outputs: 2

Exporting Individually with exports

Another way to export multiple values is to add each value to the exports object individually. This is more concise and allows for selective exporting of module components.

// utils.js
exports.sayHello = () => 'Hello, world!';
exports.sayGoodbye = () => 'Goodbye, world!';
exports.currentTime = () => new Date().toLocaleTimeString();

You can import and use these exports as follows:

// app.js
const { sayHello, sayGoodbye, currentTime } = require('./utils');

console.log(sayHello());      // Outputs: Hello, world!
console.log(sayGoodbye());    // Outputs: Goodbye, world!
console.log(currentTime());   // Outputs: current time in locale format

Conclusion

Exporting multiple values from a Node.js module can be done in various ways, each with its own advantages. Using module.exports to export an object is the most common and flexible approach, but you can also use the exports object for individual exports or mix both methods. Understanding these different approaches allows you to write modular, maintainable, and reusable code, enhancing the overall quality and scalability of your Node.js applications.