docs: function clearSelection () {
                      if ($window.getSelection) {
                          if ($window.getSelection().empty) {  // Chrome
                              $window.getSelection().empty();
                          } else if ($window.getSelection().removeAllRanges) {  // Firefox
                              $window.getSelection().removeAllRanges();
                          }
                      } else if ($document.selection) {  // IE?
                          $document.selection.empty();
                      }
                  }