Usage reselect in Redux reducers

Using reselect in reducers

// We're adding COMPLETE_ALL_VISIBLE_TODOS and DELETE_ALL_VISIBLE_TODOS 
// to the reducers.js example of ReduxExample: Todo List
// http://rackt.org/redux/docs/basics/ExampleTodoList.html > reducers.js
// using the visibleTodosSelector of Computing Derived Data
// http://rackt.org/redux/docs/recipes/ComputingDerivedData.html
// Using this memoized selector function enables reuse of derived data

import {visibleTodosSelector} from 'selectors/TodoSelectors.js';

function todos(state = [], action) {
  switch (action.type) {
  case COMPLETE_ALL_VISIBLE_TODOS: 
    const visibleTodos = visibleTodosSelector(state).visibleTodos;
    // mark all these todos as completed
    break;
  case DELETE_ALL_VISIBLE_TODOS: 
    const visibleTodos = visibleTodosSelector(state).visibleTodos;
    // delete all these todos
    break;
  // ... other cases
  default:
    return state;
  }
}