JavaScript module formats -- CJS, AMD, UMD, ESM, and IIFE

js-module-formats.md

🟤 CJS (CommonJS)

• Used by: Node.js
• Syntax: require() / module.exports
• Example:

  const fs = require('fs');
  module.exports = someFunction;

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🟠 AMD (Asynchronous Module Definition)

• Used by: Older browsers (via RequireJS)
• Syntax: define()
• Example:

  define(['dep'], function(dep) {
    return function() {};
  });

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⚪ UMD (Universal Module Definition)

• Used by: Libraries that work everywhere (browser, Node)
• Syntax: A wrapper that supports CJS, AMD, or globals
• Goal: Compatibility

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🟢 ESM (ECMAScript Modules)

• Used by: Modern browsers & Node.js
• Syntax: import / export
• Example:

  import fs from 'fs';
  export default someFunction;

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🟣 IIFE (Immediately Invoked Function Expression)

• Used by: Older scripts, no module system
• Syntax: Self-running function
• Example:

  (function() {
    // code here
  })();