Watching A Collection Of Expressions Using Scope.$watchGroup() In AngularJS

Since the early days, AngularJS has provided us with the Scope.$watch() method as a means to observe changes in the View-Model. Then, they added the Scope.$watchCollection() to perform a shallow-watch or arrays. Now, in AngularJS 1.3, they've added Scope.$watchGroup(). This new method watches a collection of expressions and then invokes the callback if any one of the expression results changes.