rng-browser.js

// Unique ID creation requires a high quality random # generator. In the browser we therefore
// require the crypto API and do not support built-in fallback to lower quality random number
// generators (like Math.random()).

// getRandomValues needs to be invoked in a context where "this" is a Crypto implementation. Also,
// find the complete implementation of crypto (msCrypto) on IE11.
const getRandomValues =
  (typeof crypto !== 'undefined' &&
    crypto.getRandomValues &&
    crypto.getRandomValues.bind(crypto)) ||
  (typeof msCrypto !== 'undefined' &&
    typeof msCrypto.getRandomValues === 'function' &&
    msCrypto.getRandomValues.bind(msCrypto));

const rnds8 = new Uint8Array(16);

export default function rng() {
  if (!getRandomValues) {
    throw new Error(
      'crypto.getRandomValues() not supported. See https://github.com/uuidjs/uuid#getrandomvalues-not-supported'
    );
  }

  return getRandomValues(rnds8);
}