You used both a subject and an observable created with fromEvent, why use both?
Why not use the operators directly on the observable?
Also you have a memory leak you create a subscription from the observable and the subject and you only unsubscribe from one of them.
https://github.com/DimaFr/angular-advanced-ex1/blob/046887da1992d0d186d8eff5f36747ee8dc9f4bf/projects/throttling/src/app/directives/tasks.directive.ts#L14
https://github.com/DimaFr/angular-advanced-ex1/blob/046887da1992d0d186d8eff5f36747ee8dc9f4bf/projects/throttling/src/app/directives/tasks.directive.ts#L30
You used both a subject and an observable created with fromEvent, why use both? Why not use the operators directly on the observable? Also you have a memory leak you create a subscription from the observable and the subject and you only unsubscribe from one of them.