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JavaScript
Modular Code

Learn to build scalable applications by splitting code into reusable ES6 Modules. Master the use of export, import, and defaults.

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Tutor:As JavaScript applications grow, keeping everything in one file becomes a nightmare. We need a way to split code into smaller, reusable pieces.


Skill Matrix

UNLOCK NODES BY LEARNING MODULE MECHANICS.

Concept: Export

To share a variable or function outside a file, you must export it. By default, everything in a module file is private to that file.

System Check

What happens to variables declared in a module that are NOT exported?

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JavaScript Modular Code

Author

Pascual Vila

Frontend Instructor // Code Syllabus

In the early days of JavaScript, scripts were just long files attached to HTML pages. As applications grew into complex SPAs (Single Page Applications), this became unmaintainable. Enter ES6 Modules.

Why Modularize?

Modules allow you to break your code into manageable, independent files. This provides encapsulation (variables in a module don't leak into the global window object by default), reusability, and dependency management.

Named vs Default Exports

There are two ways to export data from a module:

  • Named Exports: Use export const a = 1;. You can have many named exports per file. When importing, you must use curly braces: import { a } from './file.js';
  • Default Exports: Use export default Component;. You can only have ONE default export per file. You import it without braces and can name it anything: import MyComp from './file.js';

The HTML Connection

To use ES6 modules natively in the browser, you must include the script tag with thetype="module" attribute. This tells the browser to parse the file differently, enabling features like strict mode by default and deferring execution.

View CommonJS vs ES6 Notes+

Node.js historically used CommonJS modules (require() and module.exports). ES6 modules (import/export) are the modern standard for both browser and server. When working in modern frontend frameworks (React, Next.js, Vue), you will almost exclusively use ES6 module syntax.

Modules Glossary

Module

A self-contained piece of code (usually a file) that encapsulates variables and functions, preventing global scope pollution.

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Named Export

Exporting multiple values from a module. They must be imported using their exact name surrounded by curly braces.

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Default Export

The primary export of a file. Only one is allowed per module. Can be imported without curly braces and renamed at will.

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Import

The keyword used to bring in code that was exported from another module.

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Alias (as)

Used during import (or export) to rename a variable to avoid naming collisions in the current file.

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type='module'

An HTML script attribute required to let the browser know the JavaScript file contains ES6 module syntax.

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