denoland-deno/std/uuid/v4.ts

// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.

const UUID_RE = new RegExp(
  "^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$",
  "i"
);

export function validate(id: string): boolean {
  return UUID_RE.test(id);
}

export default function generate(): string {
  const rnds = crypto.getRandomValues(new Uint8Array(16));

  rnds[6] = (rnds[6] & 0x0f) | 0x40; // Version 4
  rnds[8] = (rnds[8] & 0x3f) | 0x80; // Variant 10

  const bits: string[] = [...rnds].map((bit): string => {
    const s: string = bit.toString(16);
    return bit < 0x10 ? "0" + s : s;
  });
  return [
    ...bits.slice(0, 4),
    "-",
    ...bits.slice(4, 6),
    "-",
    ...bits.slice(6, 8),
    "-",
    ...bits.slice(8, 10),
    "-",
    ...bits.slice(10)
  ].join("");
}