MIT License

async analytics.js

// Create a queue to push events and stub all methods
window.analytics || (window.analytics = {});
window.analytics_queue || (window.analytics_queue = []);
(function() {
  var methods = ['identify', 'track', 'trackLink', 'trackForm', 'trackClick', 'trackSubmit', 'page', 'pageview', 'ab', 'alias', 'ready', 'group', 'on', 'once', 'off'];

  var factory = function(method) {
    return function () {
      var args = Array.prototype.slice.call(arguments);
      args.unshift(method);
      analytics_queue.push(args);
      return window.analytics;
    };
  };

  for (var i = 0; i < methods.length; i++) {
    var method = methods[i];
    window.analytics[method] = factory(method);
  }
})();

// Load analytics.js after everything else
analytics.load = function(callback) {
  var script = document.createElement('script');
  script.async = true;
  script.type = 'text/javascript';
  script.src = '/assets/js/analytics.min.js';     // <--- your url here
  if (script.addEventListener) {
    script.addEventListener('load', function(e) {
      if (typeof callback === 'function') {
        callback(e);
      }
    }, false);
  } else {  // IE8
    script.onreadystatechange = function () {
      if (this.readyState == 'complete' || this.readyState == 'loaded') {
        callback(window.event);
      }
    };
  }
  var firstScript = document.getElementsByTagName('script')[0];
  firstScript.parentNode.insertBefore(script, firstScript);
};

analytics.load(function() {
  analytics.initialize({
    'Google Analytics': {
       trackingId: 'UA-XXX-1'
     },
     'Mixpanel': {
       token: 'XXX'
     }
  });

  // Loop through the interim analytics queue and reapply the calls to their
  // proper analytics.js method.
  while (window.analytics_queue.length > 0) {
    var item = window.analytics_queue.shift();
    var method = item.shift();
    if (analytics[method]) analytics[method].apply(analytics, item);
  }
});

@Gatsby Users: just published the related plugin https://github.com/thebarty/gatsby-plugin-analytics-without-segment