Awesome react application, wanna invest?

App.js

import React, { Component } from "react";
import "./App.css";

const names = [
  "Repe",
  "Pera",
  "Kartsa",
  "Raipe",
  "Simo",
  "Jussi",
  "Kalle",
  "Tero"
];

class App extends Component {
  state = {
    people: [{ name: "Antti", age: 28 }, { name: "Vesku", age: 30 }],
    timer: null
  };

  componentDidMount = () => {
    this.setState({
      timer: window.setInterval(this.addPerson, 1000)
    });
  };

  stop = () => {
    window.clearInterval(this.state.timer);
    this.setState({ timer: null });
  };

  generateRandomPerson = () => {
    return {
      name: names[Math.floor(Math.random() * names.length)],
      age: Math.floor(Math.random() * 20)
    };
  };

  addPerson = () => {
    const randomNewPerson = this.generateRandomPerson();
    this.setState({
      // people: this.state.people.concat(randomNewPerson)
      people: [randomNewPerson].concat(this.state.people)
    });
  };

  render() {
    console.log(this.state);
    return (
      <div className="App">
        <h1>Moimoi</h1>
        <button onClick={this.addPerson}>Paina tästä!</button>
        <button onClick={this.stop}>Apua saatana!</button>
        <div
          style={{
            display: "flex",
            flexDirection: "row",
            justifyContent: "center"
          }}
        >
          <ul>
            <div>Kaikki</div>
            {this.state.people.map((person, i) => (
              <Person name={person.name} age={person.age} key={i} />
            ))}
          </ul>

          <ul>
            <div>Vaan yli 7-vuotiaat</div>
            {this.state.people
              .filter(person => person.age > 7)
              .map((person, i) => (
                <Person name={person.name} age={person.age} key={i} />
              ))}
          </ul>

          <ul>
            <div>Vaan ne jotka alkaa äRRRällä</div>
            {this.state.people
              .filter(person => person.name[0] === "R")
              .map((person, i) => (
                <Person name={person.name} age={person.age} key={i} />
              ))}
          </ul>

          <ul>
            <div>Vaan yli nelikirjaimiset</div>
            {this.state.people
              .filter(person => person.name.length > 4)
              .map((person, i) => (
                <Person name={person.name} age={person.age} key={i} />
              ))}
          </ul>
        </div>
      </div>
    );
  }
}

export default App;

const Person = props => (
  <li>
    {props.name} {props.age}
  </li>
);