code: function getYouTubeVideoId(string) {
      if (typeof string !== 'string') {
          throw new TypeError('First argument must be a string.');
      }
      var match = string.match(regex);
      if (match && match.length > 1) {
          return match[2];
      }
      return string;
  }
docs: Get the YouTube video ID from a url or string.
  
  @param  {String} string - The url or string.
  @return {String}        - The video ID.