code: function urlToId(hypemUrl) {
          var trimmedUrl = _.trim(hypemUrl);
          if (_.startsWith(trimmedUrl, HYPEM_TRACK_URL)) {
              var parsedUrl = url.parse(hypemUrl);
              var pathname = parsedUrl.pathname; // '/trach/31jfi/...'
              var hypemId = pathname.split("/")[2];
              return hypemId;
          }
          return "";
      }
docs: Extract the hypem id from a song's url.
  
  @param {string} hypemUrl the url to extract the id
  @returns {string} the id or "" if no id was found