@Cancelable

cancelable.decorator.ts

export function cancelable() : MethodDecorator {

  return function ( target : any, propertyKey : string, descriptor : PropertyDescriptor ) {
  
    const originalFn = descriptor.value;
    const subject = new BehaviorSubject(undefined);
    const result$ = subject.asObservable().switchMap(args => originalFn(...args));
    
    descriptor.value = (...args) => {
      subject.next(args);
      return result$;
    };
    
    return descriptor;

  };

}