How to do variable tracking in angular 4?

Question

Angular

There is a variable
@Input('isActive') public isActive: boolean;
How to make tracking of its change.
In 1-x it was possible to do this
$scope.$watch('isActive' ...)

Answer 1

ngOnChanges in the controller. the first has an analogue of $onChanges. by the way $watch is deprecated in the latest versions of one