Optimizing the application using reference $watch

Reference watches register a listener that uses strict equality (===) as the comparator, which verifies the congruent object identity or primitive equality. The implication of this is that a change will only be registered if the model the watcher is listening to is assigned to a new object.

How to do it…

The reference watcher should be used when the object's properties are unimportant. It is the most efficient of the $watch types as it only demands top-level object comparison.

The watcher can be created as follows:

$scope.myObj = {
  myPrim: 'Go Bears!',
  myArr: [3,1,4,1,5,9]
};

// watch myObj by reference
$scope.$watch('myObj', function(newVal, oldVal, scope) {
  // callback logic
});

// watch only the myPrim property of myObj by reference
$scope.$watch('myObj.myPrim', function(newVal, oldVal, scope) {
  // callback logic
});

// watch only the second element of myObj.myArr by reference
$scope.$watch('myObj.myArr[1]', function(newVal, oldVal...