docs: function getSource(url) {
          if (typeof url !== 'string') {
              return [];
          }
  
          if (!_has(sourceCache, url)) {
              // URL needs to be able to fetched within the acceptable domain.  Otherwise,
              // cross-domain errors will be triggered.
              /*
                  Regex matches:
                  0 - Full Url
                  1 - Protocol
                  2 - Domain
                  3 - Port (Useful for internal applications)
                  4 - Path
              */
              var source = '';
              var domain = '';
              try { domain = window.document.domain; } catch (e) { }
              var match = /(.*)\:\/\/([^:\/]+)([:\d]*)\/{0,1}([\s\S]*)/.exec(url);
              if (match && match[2] === domain) {
                  source = loadSource(url);
              }
              sourceCache[url] = source ? source.split('\n') : [];
          }
  
          return sourceCache[url];
      }