redux blog - initialState with reselect

initialState.js

import { createSelector } from "reselect";

const initialState = {
  app: {
    users: [{ id: "user01", name: "John" }, { id: "user02", name: "Bob" }],
    tasks: [
      { id: "task01", title: "Wash car", assignee: "user01" },
      { id: "task02", title: "Watch tutorial", assignee: "user01" },
      { id: "task03", title: "Do Homework", assignee: "user02" }
    ]
  },
  ui: { /* ... */ }
}

const getUsers = state => state.app.users;
const getTasks = state => state.app.tasks;

const getUserTasks = createSelector([getUsers, getTasks], (users, tasks) => {
  return users.map(user =>
    Object.assign({}, user, {
      tasks: tasks.filter(task => task.assignee === user.id)
    })
  );
});

function userTasksCount() {
  return this.userTasks.map(user =>
    Object.assign({}, user, { tasksCount: user.tasks.count })
  );
}

Object.defineProperty(initialState, "userTasks", {
  get: function() {
    return getUserTasks(this);
  },
  enumerable: false
});

Object.defineProperty(initialState, "userTasksCount", {
  get: userTasksCount,
  enumerable: false
});

export default initialState;