Question

Does anyone know if the reasoning behind the use of dollar methods and variables in angularJS is to instruct angularJS to avoid checking those values when a digestion is going on? So, if angular comes across $scope.$value and $scope.value, then it will avoid checking the former since it’s prefixed with a dollar character in its variable name?

Answer 1

There are a few times Angular ignores variables prefixed with the dollar sign:

1. In Schumli’s comment below, where json filters will not output them

2. When using the {{ }} directive, angular will not show nested $
   variables. For example this only displays the visible property.

   <div ng-init="n = { visible: 'foo', $ignore: 'bar' };">{{ n }}</div>
   

3. Additionally when adding an explicit watcher on a scope object, changes to properties with a leading dollar sign of this object will not trigger the watcher. See this updated fiddle.

4. angular.equals() ignores keys prefixed with $.