Cookieless Google Analytics.js

// Generate random Client ID
function uuid() {
  var uuid = ( [1e7]+-1e3+-4e3+-8e3+-1e11 ).replace( /[018]/g, c => (c ^ crypto.getRandomValues(new Uint8Array(1))[0] & 15 >> c / 4).toString(16) );
  return uuid;
}

(function() {
  var ua = navigator.userAgent || navigator.vendor || window.opera;
  var clientID = uuid();
  var trackingID = 'UA-XXXXXX-YY';
  var url = 'https://www.google-analytics.com/collect';
  var payload = '?v=1' +
    '&t=pageview' +
    '&tid=' + trackingID +
    '&cid=' + clientID +
    '&dl=' + document.location.href +
    '&dt=' + document.title +
    '&dr=' + document.referrer +
    '&aip=1' +
    '&ua=' + ua;
  var xhr = new XMLHttpRequest();
  xhr.open('GET', url + payload);
  xhr.send();
})();