Shallow watches the properties of an object and fires whenever any of the properties change (for arrays this implies watching the array items, for object maps this implies watching the properties). If a change is detected the listener callback is fired.

• The obj collection is observed via standard $watch operation and is examined on every call to $digest() to see if any items have been added, removed, or moved.
• The listener is called whenever anything within the obj has changed. Examples include adding new items into the object or array, removing and moving items around.

Example

          $scope.names = ['igor', 'matias', 'misko', 'james'];
          $scope.dataCount = 4;

          $scope.$watchCollection('names', function(newNames, oldNames) {
            $scope.dataCount = newNames.length;
          });

          expect($scope.dataCount).toEqual(4);
          $scope.$digest();

          //still at 4 ... no changes
          expect($scope.dataCount).toEqual(4);

          $scope.names.pop();
          $scope.$digest();

          //now there's been a change
          expect($scope.dataCount).toEqual(3);

Scope#$watchCollection(obj, listener);