UUID v4 v JavaScriptu — generování a validace

// Funguje v jakémkoliv moderním prohlížeči — žádný build krok, žádný bundler
const requestId = crypto.randomUUID();
console.log(requestId);
// "3e7f1a92-4b0c-4d8e-9f12-7a6b3c8d5e1f"

// Použijte kdekoliv potřebujete jedinečný identifikátor
const telemetryEvent = {
  event_id: crypto.randomUUID(),
  action: "checkout.started",
  session_id: crypto.randomUUID(),
  timestamp: Date.now(),
  cart_total_cents: 14999,
};
console.log(JSON.stringify(telemetryEvent, null, 2));

// Přístup 1: globální crypto (Node.js 19+)
const orderId = crypto.randomUUID();
console.log(orderId);
// "a1b2c3d4-e5f6-4a7b-8c9d-0e1f2a3b4c5d"

// Přístup 2: explicitní import z node:crypto
import { randomUUID } from 'node:crypto';
const correlationId = randomUUID();
console.log(correlationId);
// "f7e6d5c4-b3a2-4190-8f7e-6d5c4b3a2190"

function generateUUIDv4() {
  // Preferujte nativní API, pokud je dostupné
  if (typeof crypto !== 'undefined' && typeof crypto.randomUUID === 'function') {
    return crypto.randomUUID();
  }

  // Ruční fallback pomocí getRandomValues (viz další sekce)
  const bytes = new Uint8Array(16);
  crypto.getRandomValues(bytes);

  // Nastavit verzi (4) a variantu (RFC 4122)
  bytes[6] = (bytes[6] & 0x0f) | 0x40; // version 4
  bytes[8] = (bytes[8] & 0x3f) | 0x80; // variant 10xx

  const hex = [...bytes].map(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, 16).join(''),
  ].join('-');
}

console.log(generateUUIDv4());
// "9b2e4f1a-7c3d-4e8f-a5b6-0d2c1e9f8a7b"

function uuidv4Manual() {
  const bytes = new Uint8Array(16);
  crypto.getRandomValues(bytes);

  // Set version: bits 12–15 of byte 6 = 0100 (version 4)
  bytes[6] = (bytes[6] & 0x0f) | 0x40;

  // Set variant: bits 6–7 of byte 8 = 10 (RFC 4122)
  bytes[8] = (bytes[8] & 0x3f) | 0x80;

  const hex = [...bytes].map(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, 16).join('')
  );
}

const traceId = uuidv4Manual();
console.log(traceId);
// "e4d7c2a1-3f9b-48e5-a612-9d8c7b6a5f4e"

// Verify it passes UUID v4 validation
const UUID_V4_RE = /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i;
console.log(UUID_V4_RE.test(traceId)); // true

npm install uuid

import { v4 as uuidv4, validate, version } from 'uuid';

// Generate a UUID v4
const paymentId = uuidv4();
console.log(paymentId);
// "1b9d6bcd-bbfd-4b2d-9b5d-ab8dfbbd4bed"

// Validate any UUID string
console.log(validate(paymentId));    // true
console.log(validate("not-a-uuid")); // false

// Detect the version of a UUID
console.log(version(paymentId));     // 4

// Generate a batch for seeding a test database
const testAccounts = Array.from({ length: 5 }, () => ({
  account_id: uuidv4(),
  plan: "starter",
  created_at: new Date().toISOString(),
}));
console.log(testAccounts);

import { v5 as uuidv5 } from 'uuid';

// Built-in namespace for URLs (RFC 4122)
const URL_NAMESPACE = uuidv5.URL;
// "6ba7b811-9dad-11d1-80b4-00c04fd430c8"

// Same URL always produces the same UUID
const pageId1 = uuidv5("https://api.warehouse.dev/products/sku-7291", URL_NAMESPACE);
const pageId2 = uuidv5("https://api.warehouse.dev/products/sku-7291", URL_NAMESPACE);
console.log(pageId1 === pageId2); // true
console.log(pageId1);
// "a6e4e1c0-7e23-5d3b-8f14-9c2a1b3d5e7f"

// Custom namespace for your application
const APP_NAMESPACE = "f47ac10b-58cc-4372-a567-0e02b2c3d479";
const tenantId = uuidv5("acme-corp", APP_NAMESPACE);
console.log(tenantId);
// "d4735e3a-265b-564e-8f32-7a1b2c3d4e5f"

const UUID_V4_RE = /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i;

function isUUIDv4(str) {
  return UUID_V4_RE.test(str);
}

// Valid UUID v4
console.log(isUUIDv4("9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d")); // true

// UUID v1 — version nibble is 1, not 4
console.log(isUUIDv4("550e8400-e29b-11d4-a716-446655440000")); // false

// UUID v7 — version nibble is 7
console.log(isUUIDv4("018e4a0c-5b3f-7d12-8a9b-0c1d2e3f4a5b")); // false

// Malformed strings
console.log(isUUIDv4("not-a-uuid"));           // false
console.log(isUUIDv4(""));                      // false
console.log(isUUIDv4("9b1deb4d3b7d4bad9bdd2b0d7b3dcb6d")); // false (no hyphens)

// Extract UUID from a larger string
const logLine = 'Request req_id=9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d failed with 503';
const match = logLine.match(/[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}/i);
console.log(match?.[0]);
// "9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d"

import { readFileSync, writeFileSync } from 'node:fs';
import { randomUUID } from 'node:crypto';

function assignIds(inputPath, outputPath) {
  const lines = readFileSync(inputPath, 'utf-8')
    .split('\n')
    .filter(line => line.trim());

  const records = lines.map(line => {
    try {
      const record = JSON.parse(line);
      if (!record.id) {
        record.id = randomUUID();
      }
      return JSON.stringify(record);
    } catch (err) {
      console.error(`Skipping malformed line: ${err.message}`);
      return null;
    }
  }).filter(Boolean);

  writeFileSync(outputPath, records.join('\n') + '\n');
  console.log(`Assigned IDs to ${records.length} records → ${outputPath}`);
}

assignIds('warehouse-products.ndjson', 'warehouse-products-with-ids.ndjson');
// Assigned IDs to 1284 records → warehouse-products-with-ids.ndjson

import { randomUUID } from 'node:crypto';

async function createShipment(orderPayload) {
  const correlationId = randomUUID();

  try {
    const response = await fetch('https://api.logistics.dev/v2/shipments', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'X-Correlation-ID': correlationId,
        'X-Idempotency-Key': randomUUID(),
      },
      body: JSON.stringify(orderPayload),
    });

    if (!response.ok) {
      const errorBody = await response.text();
      throw new Error(`Shipment API returned ${response.status}: ${errorBody}`);
    }

    const result = await response.json();
    console.log(`Shipment created: ${result.shipment_id} (correlation: ${correlationId})`);
    return result;
  } catch (err) {
    console.error(`[correlation:${correlationId}] Shipment failed: ${err.message}`);
    throw err;
  }
}

await createShipment({
  order_id: "ord_8a3f91bc",
  destination: { city: "Praha", state: "CZ", zip: "11000" },
  items: [{ sku: "WH-7291", quantity: 2, weight_kg: 1.4 }],
});

# Single UUID
node -e "console.log(crypto.randomUUID())"
# 3e7f1a92-4b0c-4d8e-9f12-7a6b3c8d5e1f

# Five UUIDs at once
node -e "for(let i=0;i<5;i++) console.log(crypto.randomUUID())"

# Generate and assign to a shell variable
export REQUEST_ID=$(node -e "process.stdout.write(crypto.randomUUID())")
echo "Request ID: $REQUEST_ID"

# Use npx uuid (if you have the package installed globally or want a one-off)
npx uuid v4
# 1b9d6bcd-bbfd-4b2d-9b5d-ab8dfbbd4bed

# Open any browser DevTools console and type:
crypto.randomUUID()
# "9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d"

npm install nanoid

import { nanoid, customAlphabet } from 'nanoid';

// Default: 21-char URL-safe ID (A-Za-z0-9_-)
const trackingCode = nanoid();
console.log(trackingCode);
// "V1StGXR8_Z5jdHi6B-myT"

// Custom length
const shortCode = nanoid(10);
console.log(shortCode);
// "IRFa-VaY2b"

// Custom alphabet — numbers only, 12 digits
const numericId = customAlphabet('0123456789', 12);
console.log(numericId());
// "839274651023"

// Custom alphabet — hex only, 32 chars (same entropy as UUID v4 without hyphens)
const hexId = customAlphabet('0123456789abcdef', 32);
console.log(hexId());
// "4f8a1b2c3d7e9f0a5b6c8d1e2f3a4b5c"

import chalk from 'chalk';
import { randomUUID } from 'node:crypto';

function logEvent(action, metadata = {}) {
  const eventId = randomUUID();
  const timestamp = new Date().toISOString();

  console.log(
    chalk.gray(timestamp),
    chalk.cyan(eventId),
    chalk.white(action),
    Object.keys(metadata).length
      ? chalk.dim(JSON.stringify(metadata))
      : ''
  );
}

logEvent('shipment.created', { order_id: 'ord_8a3f', carrier: 'fedex' });
logEvent('payment.captured', { amount_cents: 14999, currency: 'USD' });
logEvent('webhook.delivered', { endpoint: 'https://hooks.acme.dev/orders' });
// 2026-03-27T10:15:00.000Z  a1b2c3d4-...  shipment.created  {"order_id":"ord_8a3f",...}

import { randomUUID } from 'node:crypto';

// 1. Strip hyphens from UUID v4 → 32-char hex string
const hex32 = randomUUID().replaceAll('-', '');
console.log(hex32);
// "3e7f1a924b0c4d8e9f127a6b3c8d5e1f" (32 chars)

// 2. Base64-encode 16 random bytes → 22-char string (URL-safe)
const bytes = new Uint8Array(16);
crypto.getRandomValues(bytes);
const base64Id = Buffer.from(bytes)
  .toString('base64url')
  .replace(/=+$/, '');
console.log(base64Id);
// "Pj8akksNTY6fEnarPIvR" (22 chars, 128 bits of entropy)

// 3. nanoid at custom length
import { nanoid } from 'nanoid';
const short12 = nanoid(12);
console.log(short12);
// "V1StGXR8_Z5j" (12 chars, ~71 bits of entropy)

import { v7 as uuidv7 } from 'uuid';

// Generate three UUID v7 values — notice they sort chronologically
const id1 = uuidv7();
const id2 = uuidv7();
const id3 = uuidv7();

console.log(id1);
// "018e4a0c-5b3f-7d12-8a9b-0c1d2e3f4a5b"
console.log(id2);
// "018e4a0c-5b40-7e34-9c2d-1e4f5a6b7c8d"
console.log(id3);
// "018e4a0c-5b41-7f56-ae3f-2a5b6c7d8e9f"

// They sort lexicographically by creation time
console.log([id3, id1, id2].sort());
// [id1, id2, id3] — chronological order preserved

// Use v4 for tokens where timing should not be leaked
import { v4 as uuidv4 } from 'uuid';
const sessionToken = uuidv4(); // fully random, no timing info

<!DOCTYPE html>
<html lang="en">
<head><meta charset="utf-8"><title>UUID Generator</title></head>
<body>
  <p>Your UUID: <strong id="output"></strong></p>
  <button onclick="document.getElementById('output').textContent = crypto.randomUUID()">
    Generate
  </button>
  <script>
    // Generate one on page load
    document.getElementById('output').textContent = crypto.randomUUID();
  </script>
</body>
</html>