AngularJS and its use of Dollar Variables

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

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.

   {{ n }}

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 $.