generateRandomUUID.js

// generateRandomUUID.js
// https://github.com/DavidAnson/generateRandomUUID
// 2019-10-27

"use strict";

// JavaScript code to efficiently generate a random UUID per RFC 4122
function generateRandomUUID() {
  // UUIDs have 16 byte values
  const bytes = new Uint8Array(16);
  // Seed bytes with cryptographically random values
  crypto.getRandomValues(bytes);
  // Set required fields for an RFC 4122 random UUID
  bytes[6] = (bytes[6] & 0x0f) | 0x40;
  bytes[8] = (bytes[8] & 0x3f) | 0x80;
  // Convert bytes to hex and format appropriately
  const uuid = Array.prototype.map.call(bytes, (b, i) => {
    // Left-pad single-character values with 0,
    // Convert to hexadecimal,
    // Add dashes
    return ((b < 16) ? "0" : "") +
      b.toString(16) +
      (((i % 2) && (i < 10) && (i > 2)) ? "-" : "");
  }).join("");
  // Return the string
  return uuid;
}