# Javascript Modules

• Overview
• CommonJS Modules
  • Exporting a Module
  • Importing a Module
• ECMAScript modules
  • Named exports and imports
  • Default exports and imports

# Overview

JavaScript modules are a way to split JavaScript code into separate files, each of which can export or import variables, functions, classes, or values from or to other modules. This allows for better organization, reusability, and separation of concerns in your code.

There are two types of modules in JavaScript: CommonJS and ECMAScript modules.

# CommonJS Modules

CommonJS is a module system used primarily in Node.js environments. It allows you to define modules using module.exports to export values, functions, or objects from a file.

# Exporting a Module

To export a module in CommonJS, use module.exports to export values, functions, or objects.

module.exports = {
    getName: (user) => user.name,
    getAge: (user) => user.age
};

# Importing a Module

To import a CommonJS module, use require to import and access exported values, functions, or objects. There are two ways to import a module in CommonJS.

1. You can import the entire module into a single variable:

const user = require('./user.js');

In this case, you would access the exported functions like this: user.getName() and user.getAge().

2. You can use destructuring to import specific functions:

const { getName, getAge } = require('./user.js');

With this method, you can call the functions directly: getName() and getAge().

# ECMAScript modules

ES modules are the standard for modern JavaScript and are supported in browsers as well as recent versions of Node.js. They use export and import statements to manage how module content is exposed and imported.

# Named exports and imports

Named exports allow you to selectively export multiple values, functions, or classes from a module. Each exported item is identified by its name.

export let getName = (user) => user.name;
export let getAge = (user) => user.age;

To import named exports, use the import statement followed by the names of the exported items enclosed in curly braces {}.

import { getName, getAge } from './user.js';

# Default exports and imports

A module can have a single default export, typically representing the main functionality or value of the module.

export default class User {
    constructor(name, age) {
        this.name = name;
        this.age = age;
    }
}

To import a default export, use the import statement followed by the name of the exported item, which can be any name you choose.

import User from './path/to/user';