analytics.js load routine annotated

snippet.js

// Create a queue, but don't obliterate an existing one!
var analytics = analytics || [];

(function () {

  // A list of all the methods we want to generate queueing stubs for.
  var methods = [
    'identify', 'track', 'trackLink', 'trackForm', 'trackClick', 'trackSubmit',
    'page', 'pageview', 'ab', 'alias', 'ready', 'group'
  ];

  // For each of our methods, generate a queueing method that pushes arrays of
  // arguments onto our `analytics` queue. The first element of the array
  // is always the name of the analytics.js method itself (eg. `track`), so that
  // we know where to replay them when analytics.js finally loads.
  var factory = function (method) {
    return function () {
      analytics.push([method].concat(Array.prototype.slice.call(arguments, 0)));
    };
  };

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

}());

// Define a method that will asynchronously load analytics.js from our CDN.
analytics.load = function(apiKey) {

  // Create an async script element for analytics.js based on your API key.
  var script = document.createElement('script');
  script.type = 'text/javascript';
  script.async = true;
  script.src = ('https:' === document.location.protocol ? 'https://' : 'http://') +
                'd2dq2ahtl5zl1z.cloudfront.net/analytics.js/v1/' + apiKey + '/analytics.min.js';

  // Find the first script element on the page and insert our script next to it.
  var firstScript = document.getElementsByTagName('script')[0];
  firstScript.parentNode.insertBefore(script, firstScript);
};

// Load analytics.js with your API key, which will automatically load all of the
// analytics integrations you've turned on for your account. Boosh!
analytics.load('REDACTED');