redux - map state to props example

usersMapping.jsx

/* initialState.js */
const books = [ /* ... */ ]
const users = [ /* ... */ ]
const comments = [ /* ... */ ];

const usersSummary = function() {
  return this.users.map(user => ({
    ...user,
    booksCount: user.books.length,
    commentsCount: this.comments.filter(c => c.user === user.id).length
  }));
};

export const initialState = {
  books,
  users,
  comments,
  get usersSummary() {
    return usersSummary.call(this);
  }
};

/* Users.js component */
import React from "react";
import { connect } from "react-redux";

const Users = ({ users }) => (/* ... */);

const mapStateToProps = ({ usersSummary }) => ({ users: usersSummary });

export default connect(mapStateToProps)(Users);