In JavaScript, modules are encapsulated pieces of code that help in organizing, separating, and reusing code within a program. Modules enable developers to break down a large codebase into smaller, more manageable parts, each with its own scope, dependencies, and functionality.
Characteristics of Modules:- Encapsulation: Modules encapsulate related functions, variables, or classes, keeping their implementation details private and exposing only necessary functionalities through an exported interface.
- Dependency Management: They help manage dependencies by allowing modules to import and use functionalities or data exported by other modules, promoting better code reuse and maintainability.
- Separation of Concerns: Modules encourage the separation of different functionalities, allowing developers to focus on specific parts of an application without worrying about the entire codebase.
- Scoping: Modules have their own scope, preventing variables and functions from conflicting with similarly named entities in other modules.
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ES6 Modules (ESM):
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Officially introduced in ES6 (ECMAScript 2015), ESM provides a standardized module system for JavaScript, using
import and export
keywords to define dependencies and export functionalities. - Example:
// Exporting module // utils.js export function add(a, b) { return a + b; } // Importing module // main.js import { add } from './utils.js'; console.log(add(2, 3)); // Output: 5
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Officially introduced in ES6 (ECMAScript 2015), ESM provides a standardized module system for JavaScript, using
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CommonJS Modules (CJS):
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CommonJS is a module format used in Node.js. It uses
require()
to import modules andmodule.exports
to export functionalities. - Example:
// Exporting module // utils.js function add(a, b) { return a + b; } module.exports = { add }; // Importing module // main.js const { add } = require('./utils.js'); console.log(add(2, 3)); // Output: 5
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CommonJS is a module format used in Node.js. It uses
- Code Reusability: Modules promote code reuse by allowing the same functionalities to be used across different parts of an application or even in different applications.
- Maintainability: They make codebases more maintainable by organizing code into smaller, focused units, making it easier to understand, update, and debug.
- Reduced Global Scope Pollution: Modules help reduce global scope pollution by encapsulating code within their own scope, minimizing the risk of variable clashes and unintended side effects.
Modules play a vital role in modern JavaScript development, providing a structured and modular approach to building applications while improving code quality, maintainability, and scalability.