extract_url_domain.js

var _embedder = (function(doc) {
    var referrer = doc.referrer,
        anchor = doc.createElement('a'),
        res = [referrer];

    /*
        Two different ways to extract domain from url:
        - for only one part, we can use a fast regexp: referrer.match(/:\/\/(.[^/]+)/)[1])
        - for 2+ parts, create manually a '<a>' tag, set his href to the referrer url, and
          then we can access to several url infos: protocol, hostname, port...
          (@see https://gist.github.com/jlong/2428561)
    */
    anchor.href = referrer;
    res.push(anchor.protocol + '//' + anchor.hostname);

    return res.join(' | ');
}(document));