filteredTodoListState.js

const filteredTodoListState = selector({
  key: 'filteredTodoListState',
  get: ({get}) => {
    const filter = get(todoListFilterState);
    const list = get(todoListState);

    switch (filter) {
      case 'completed':
        return list.filter((item) => item.isCompleted);
      case 'uncompleted':
        return list.filter((item) => !item.isCompleted);
      default: // all
        return list;
    }
  },
});