Why do some variables start with a dollar sign?

[John Wheeler]

It didn't really catch my attention while using $scope and $rootScope, but after using formcontroller and seeing the $dirty, $pristine, and all that, I have to ask. What is the convention going on in angular when prefixing certain things with a dollar sign? Is that so they don't get mixed up with client code?

Thanks,
John

[Antonello Pasella]

http://docs.angularjs.org/guide/dev_guide.services.understanding_services

"Like other core Angular variables and identifiers, the built-in services always start with $ (such as $http mentioned above)."

[Michael Glass]

Angular's toJson and equals ignore $ prefixed vars.  Is it ok for me to use $ to set pseudo-private params on objects?  Should I consistently use $$ instead of $?

[Matthieu Larcher]

Angular prefixes its exposed variables with a $, and its internal variables with $$, so you shouldn't use either one for your code.