StatusChanges in Angular Forms
StatusChanges is an event raised by the Angular forms whenever the Angular calculates the validation status of the FormControl, FormGroup or FormArray. It returns an observable so that you can subscribe to it. The observable gets the latest status of the control. The Angular runs the validation check on every change made to the control. It also generates a list of validation errors in which case the status becomes INVALID. If there are no errors, then the status becomes VALID