code: function BINDING_anchor($scope, key, element, getControl, bindings) {
          bindings.push($scope.$watch(key, function (newValue, oldValue) {
              newValue = typeof newValue === "string" ? select(newValue, element) : newValue;
              oldValue = typeof oldValue === "string" ? select(oldValue, element) : oldValue;
              if (oldValue && oldValue._anchorClick) {
                  oldValue.removeEventListener("click", oldValue._anchorClick);
                  oldValue._anchorClick = null;
              }
              if (newValue && !newValue._anchorClick) {
                  newValue._anchorClick = function () { getControl().show(); };
                  newValue.addEventListener("click", newValue._anchorClick);
              }
              return newValue;
          }));
          var anchor = $scope[key];
          return typeof anchor === "string" ? select(anchor, element) : anchor;
      }
docs: Refer to https://docs.angularjs.org/api/ng/service/$compile for documentation on what "=?" etc. means