iframe_cross_domain_tracking_child

<script>
/*
* adapted from https://developers.google.com/analytics/devguides/collection/analyticsjs/cross-domain#iframes
* I include the GA object reference in my script, so that one version of 
* the script works whether served in an iFrame or on a standalone page. 
* I usually have to rely on the 3rd-party vendor to implement the code, so 
* I like to keep implementation as simple as possible.
*/

  (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
  (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
  m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
  })(window,document,'script','https://www.google-analytics.com/analytics.js','ga');

  var trackerCreated = false;

  function createTracker(opt_clientId) {
    if (!trackerCreated) {
      var fields = {};
      if (opt_clientId) {
        fields.clientId = opt_clientId;
      }

      ga('create', 'UA-XXXXXXXX-Y', 'auto', fields);
      // Google’s sample doesn’t do anything with the tracker
      // once created, but presumably you will want to send either a 
      // GA pageview or event, like I have here.
	ga('send', 'pageview');

      trackerCreated = true;
    }
  }

  window.addEventListener('message', function(event) {
    if (event.origin != 'http://www.xyz.com') return;
    createTracker(event.data);
  });

  // I increased the timeout to 5 seconds to give the message more
  // time to arrive.
  setTimeout(createTracker, 5000);

</script>