ExampleWithEffects.js

class ExampleWithEffects extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      count: 0
    };
    this.timer = null;
  }
  minus = () => {
    this.setState(prevState => ({
      count: prevState.count - 1
    }));
  };
  componentDidMount() {
    this.timer = setInterval(this.minus, 150);
    document.title = `You clicked ${this.state.count} times`;
  }
  componentDidUpdate() {
    document.title = `You clicked ${this.state.count} times`;
  }
  componentWillUnmount() {
    clearInterval(this.timer);
  }
  render() {
    const { count } = this.state;
    return (
      <div>
        <p>You clicked {count} times</p>
        <button onClick={() => this.setState({ count: count + 1 })}>
          Click me
        </button>
      </div>
    );
  }
}