In JavaScript, modules are self-contained units of code that can expose assets to other modules using export and consume assets from other modules using import. This mechanism is essential for building modular and reusable code in modern JavaScript applications.

Default Exports

A module can have only one default export.
To export a default asset, use the default keyword before the exported entity.
To import a default export, you can directly assign it to a variable without specifying the exported name:

// Exporting a default asset
export default function greet(name) {
  console.log(`Hello, ${name}!`);
}

// Importing the default export
import greet from './myModule';

Named Exports

A module can have multiple named exports.
To export a named asset, use the export keyword before the exported entity and give it a name.
To import named exports, you must specify the names of the assets you want to import:

// Exporting named assets
export function greet(name) {
  console.log(`Hello, ${name}!`);
}

export function farewell(name) {
  console.log(`Goodbye, ${name}!`);
}

// Importing named exports
import { greet, farewell } from './myModule';

Combining Default and Named Exports

You can have both a default export and named exports in a single module:

export default function greet(name) {
  console.log(`Hello, ${name}!`);
}

export function farewell(name) {
  console.log(`Goodbye, ${name}!`);
}

To import both the default and named exports:

import greet, { farewell } from './myModule';

Key Points to Remember

export is used to expose assets from a module.
import is used to consume assets from other modules.
A module can have only one default export.
Named exports can be imported individually or collectively.
The names used for imports are arbitrary and don't have to match the names used in the exported module.

Practical Example

Consider a React component:

import React from 'react';

export default function Greeting({ name }) {
  return <h1>Hello, {name}!</h1>;
}

In this example, the Greeting component is exported as the default export. It can be imported and used in other components:

import Greeting from './Greeting';

function MyComponent() {
  return <Greeting name="Alice" />;
}

By understanding exports and imports, you can effectively organize and reuse code in your JavaScript projects.

Understanding Exports and Imports in JavaScript