Operations on 2 separate collections v3

// use interface instead class for TS
export interface Task {
  goal_id: string;
  name: string;
  description: string;
  priority: string;
  taskDate: string;
  id: string; // key collection
}

// Base Goal Model
export interface Goal {
  name: string;
  isMainGoal: boolean;
  details: string;
  category: string;
  lifeArea: string;
  creationDate: string;
  priority: string;
  endDate: Date;
  id: string;
}



class MyService {

    getTasksByCategory(category:string):Observable<any> {
        const daysFromThisWeek = this.getDaysFromThisWeek();
        return forkJoin({
          tasks: this.tasksS.tasksCollection(),
          goals: this.goalsS.goalsCollection(),
        })
        // !!! OPERATIONS ON GOALS !!! 
        .pipe(
          // filter goals with category from parameter
          map(({ tasks, goals }) => {
            return goals.filter((item:any) => item.category === category);
          }),
          // get ID's of found goals in the previous step
          map((goals:any) => {
            const goalsIDs = goals.map((item:any) => item.id);
            return goalsIDs;
          })
        )
        // !!! OPERATIONS ON TASKS !!!
        .pipe(
          // get IDs-matching-tasks
          map(({ tasks, goalsIDs }) => {
            let modArr = [] as any;
            goalsIDs.forEach((goalId:any) => {
              const forModArr = tasks.filter((task:any) => task.goal_id === goalId);
              modArr = modArr.concat(forModArr);
          })
          return modArr;
        }),
        map(tasksArr => {
          // get number of IDs-matching-tasks on each week day
          let finalTasks = [] as any;
          daysFromThisWeek.forEach((day:any) => {
              const forFinalTasks = tasksArr.filter((task:any) => task.taskDate === day);
              finalTasks = finalTasks.concat(forFinalTasks.length);
          })
          return finalTasks;
        })
        )
    }
    
    getDaysFromThisWeek() {
        let daysArr = [];
        for(let i=1; i<=7; i++) {
          daysArr.push(dayjs().startOf('week').add(i, "day").format('YYYY-MM-DD'));
        }
        return daysArr;
    }

}