The main file that binds everything, app.js, is given as follows. The App component acts as the root file:

import React, { PureComponent } from "react";
import PropTypes from "prop-types";
import { connect } from "react-redux";

import TodoList from "./TodoList";
import AddTodo from "./AddTodo";
import Footer from "./Footer";

class App extends PureComponent {
  static propTypes = {
    activeFilter: PropTypes.string.isRequired,
    todoList: PropTypes.object.isRequired,
    dispatch: PropTypes.func.isRequired
  };

  render() {
    const { dispatch, activeFilter, todoList } = this.props;
    return (
      <div className="app">
        <div className="todos">
          <h1>Rask Lege TODO App</h1>
          <AddTodo dispatch={dispatch} />
          <TodoList
            dispatch={dispatch}
            activeFilter={activeFilter}
            todoList={todoList}
          />
          <Footer dispatch={dispatch} activeFilter={activeFilter} />
        </div>
      </div>
    );
  }
}

const mapStateToProps = state => ({ ...state.todos });

export default connect(mapStateToProps)(App);

To run the code, follow these steps:

yarn install
yarn start
# This should start the application at:
Local:            http://localhost:3000/
On Your Network:  http://10.0.20.219:3000/

Try to create some notes, mark it as done, and use the filter to see how it works.