Generates a RFC 4122 version 4 UUID using cryptographically secure random numbers.

uuidv4.js

/**
 * @file uuidv4.js
 * @description
 * Generates an RFC 4122 version 4 UUID using cryptographically secure random numbers.
 * Works in modern browsers and Node.js environments that support the global `crypto` object.
 *
 * @example
 * import { uuidv4 } from './uuidv4.js';
 * console.log(uuidv4()); // "e7b4a2c1-4f6e-4cbb-8a14-9e7bcd84f96b"
 */

/**
 * Generates cryptographically secure random bytes.
 * Falls back to Node.js `crypto.randomFillSync` if `crypto.getRandomValues` is not available.
 *
 * @param {Uint8Array} arr - A typed array to fill with random values.
 * @returns {Uint8Array} The filled array of random bytes.
 * @throws {Error} If no cryptographically secure random number generator is available.
 */
function getSecureRandomValues(arr) {
	if (typeof crypto !== 'undefined' && typeof crypto.getRandomValues === 'function') {
		// Browser or modern Node.js
		return crypto.getRandomValues(arr);
	} else if (typeof require === 'function') {
		// Fallback for older Node.js versions
		try {
			const { randomFillSync } = require('crypto');
			return randomFillSync(arr);
		} catch {
			throw new Error('No cryptographically secure random number generator available.');
		}
	} else {
		throw new Error('No cryptographically secure random number generator available.');
	}
}

/**
 * Generates a Version 4 (random) UUID as defined in RFC 4122.
 *
 * The UUID format is `xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx`, where:
 * - `x` is any hexadecimal digit.
 * - `y` is one of `8`, `9`, `A`, or `B`.
 *
 * @returns {string} A randomly generated UUIDv4 string.
 */
export function uuidv4() {
	const bytes = getSecureRandomValues(new Uint8Array(16));

	// Set version (4) and variant (10xx)
	bytes[6] = (bytes[6] & 0x0f) | 0x40;
	bytes[8] = (bytes[8] & 0x3f) | 0x80;

	const hex = Array.from(bytes, (b) => b.toString(16).padStart(2, '0'));

	return (
		`${hex.slice(0, 4).join('')}-` +
		`${hex.slice(4, 6).join('')}-` +
		`${hex.slice(6, 8).join('')}-` +
		`${hex.slice(8, 10).join('')}-` +
		`${hex.slice(10).join('')}`
	);
}

export default uuidv4;

uuidv4.mjs

/**
 * @file uuidv4.mjs
 * @description
 * Generates an RFC 4122 version 4 UUID using cryptographically secure random numbers.
 * Works in modern browsers and Node.js environments that support the global `crypto` object.
 *
 * @example
 * import { uuidv4 } from './uuidv4.mjs';
 * console.log(uuidv4()); // "e7b4a2c1-4f6e-4cbb-8a14-9e7bcd84f96b"
 */

/**
 * Generates cryptographically secure random bytes.
 * Falls back to Node.js `crypto.randomFillSync` if `crypto.getRandomValues` is not available.
 *
 * @param {Uint8Array} arr - A typed array to fill with random values.
 * @returns {Uint8Array} The filled array of random bytes.
 * @throws {Error} If no cryptographically secure random number generator is available.
 */
function getSecureRandomValues(arr) {
  if (typeof crypto !== 'undefined' && typeof crypto.getRandomValues === 'function') {
    return crypto.getRandomValues(arr); // Browser or modern Node
  } else if (typeof require === 'function') {
    // Fallback for older Node.js versions
    try {
      const { randomFillSync } = require('crypto');
      return randomFillSync(arr);
    } catch {
      throw new Error('No cryptographically secure random number generator available.');
    }
  } else {
    throw new Error('No cryptographically secure random number generator available.');
  }
}

/**
 * Generates a Version 4 (random) UUID as defined in RFC 4122.
 *
 * The UUID format is 8-4-4-4-12 hexadecimal digits, such as:
 * `xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx`
 *
 * @returns {string} A randomly generated UUIDv4 string.
 */
export function uuidv4() {
  const bytes = getSecureRandomValues(new Uint8Array(16));

  // Set version (4) and variant (10xx)
  bytes[6] = (bytes[6] & 0x0f) | 0x40;
  bytes[8] = (bytes[8] & 0x3f) | 0x80;

  const hex = Array.from(bytes, b => b.toString(16).padStart(2, '0'));
  return (
    `${hex.slice(0, 4).join('')}-` +
    `${hex.slice(4, 6).join('')}-` +
    `${hex.slice(6, 8).join('')}-` +
    `${hex.slice(8, 10).join('')}-` +
    `${hex.slice(10).join('')}`
  );
}

export default uuidv4;

uuidv4.ts

/**
 * @file uuidv4.ts
 * @description
 * Generates an RFC 4122 version 4 UUID using cryptographically secure random numbers.
 * Works in modern browsers and Node.js environments that support the global `crypto` object.
 *
 * @example
 * import { uuidv4 } from './uuidv4';
 * console.log(uuidv4()); // "e7b4a2c1-4f6e-4cbb-8a14-9e7bcd84f96b"
 */

/**
 * Generates cryptographically secure random bytes.
 * Falls back to Node.js `crypto.randomFillSync` if `crypto.getRandomValues` is not available.
 *
 * @param arr - A typed array to fill with random values.
 * @returns The filled array of random bytes.
 * @throws {Error} If no cryptographically secure random number generator is available.
 */
function getSecureRandomValues(arr: Uint8Array): Uint8Array {
	if (typeof crypto !== 'undefined' && typeof crypto.getRandomValues === 'function') {
		// Browser or modern Node.js
		return crypto.getRandomValues(arr);
	} else if (typeof require === 'function') {
		// Fallback for older Node.js versions
		try {
			const { randomFillSync } = require('crypto') as typeof import('crypto');
			return randomFillSync(arr);
		} catch {
			throw new Error('No cryptographically secure random number generator available.');
		}
	} else {
		throw new Error('No cryptographically secure random number generator available.');
	}
}

/**
 * Generates a Version 4 (random) UUID as defined in RFC 4122.
 *
 * The UUID format is `xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx`, where:
 * - `x` is any hexadecimal digit.
 * - `y` is one of `8`, `9`, `A`, or `B`.
 *
 * @returns A randomly generated UUIDv4 string.
 */
export function uuidv4(): string {
	const bytes = getSecureRandomValues(new Uint8Array(16));

	// Set version (4) and variant (10xx)
	bytes[6] = (bytes[6] & 0x0f) | 0x40;
	bytes[8] = (bytes[8] & 0x3f) | 0x80;

	const hex = Array.from(bytes, (b) => b.toString(16).padStart(2, '0'));

	return (
		`${hex.slice(0, 4).join('')}-` +
		`${hex.slice(4, 6).join('')}-` +
		`${hex.slice(6, 8).join('')}-` +
		`${hex.slice(8, 10).join('')}-` +
		`${hex.slice(10).join('')}`
	);
}

export default uuidv4;

uuidv4_OG.js

/**
 *
 * @file uuidv4.js
 * @description*
 * Generates a RFC 4122 version 4 UUID using cryptographically secure random numbers.
 * Falls back to Node.js crypto if not in a browser.
 * Throws if no cryptographically secure PRNG is available.
 *
 * Vibe coding using GitHub CoPilot and ChatGPT.
 *
 * @example
 * import { uuidv4 } from './uuidv4.js';
 * console.log(uuidv4()); // "e7b4a2c1-4f6e-4cbb-8a14-9e7bcd84f96b"
 *
 * @returns {string} The generated UUID string in the standard 8-4-4-4-12 format. // "e7b4a2c1-4f6e-4cbb-8a14-9e7bcd84f96b"
 */
(function (global, factory) {
	if (typeof module !== 'undefined' && typeof module.exports !== 'undefined') {
		// CommonJS (Node.js)
		module.exports = factory(require('crypto'));
	} else if (typeof define === 'function' && define.amd) {
		// AMD (if needed)
		define(['crypto'], factory);
	} else {
		// Browser global
		global.uuidv4 = factory(global.crypto);
	}
})(typeof globalThis !== 'undefined' ? globalThis : this, function (cryptoSource) {
	function getSecureRandomValues(arr) {
		if (cryptoSource && typeof cryptoSource.getRandomValues === 'function') {
			return cryptoSource.getRandomValues(arr); // Browser
		} else if (cryptoSource && typeof cryptoSource.randomFillSync === 'function') {
			return cryptoSource.randomFillSync(arr); // Node.js
		} else {
			throw new Error('No cryptographically secure random number generator available.');
		}
	}

	function uuidv4() {
		const bytes = getSecureRandomValues(new Uint8Array(16));

		// Set version and variant bits
		bytes[6] = (bytes[6] & 0x0f) | 0x40; // Version 4
		bytes[8] = (bytes[8] & 0x3f) | 0x80; // Variant 10xx

		const hex = Array.from(bytes, (b) => b.toString(16).padStart(2, '0'));
		return (
			`${hex.slice(0, 4).join('')}-` +
			`${hex.slice(4, 6).join('')}-` +
			`${hex.slice(6, 8).join('')}-` +
			`${hex.slice(8, 10).join('')}-` +
			`${hex.slice(10).join('')}`
		);
	}

	return uuidv4;
});