UUID v4 for browsers

uuid-v4-browser.js

/** See https://bit.ly/2gvCcqe to learn more about UUID v4 for browsers */
function uuidv4() {
  if (window.crypto && window.crypto.getRandomValues) {
    return ([1e7]+-1e3+-4e3+-8e3+-1e11).replace(/[018]/g, c =>
      (c ^ crypto.getRandomValues(new Uint8Array(1))[0] & 15 >> c / 4).toString(16));
  }

  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, (c) => {
    const r = Math.random() * 16 | 0;
    const v = c == 'x' ? r : (r & 0x3 | 0x8);
    return v.toString(16);
  });
}