Timer countdown using React

timer.js

class Timer extends React.Component {
  constructor(props) {
    super(props);
    this.state = {count: 10};
  }

  componentDidMount() {
    this.timerID = setInterval(
      () => this.tick(),
      1000
    );
  }
  
  doSomething() {
    if (this.state.count == 0) {
      clearInterval(this.timerID);
    }
  }

  tick() {
    this.setState({
      count: this.state.count - 1
    });
    this.doSomething();
  }

  render() {
    return (
      <div>
        <h1>{this.state.count}</h1>
      </div>
    );
  }
}

ReactDOM.render(
  <Timer />,
  document.getElementById('app')
);