问React: document.getElementById (或onClick)不工作

EN

class StartStream extends Component {
  state = { randomId: 0 }

  generate = () => {
    this.setState({ randomId: Math.random() * 1000 });
  }

  render() {
    return <div>
      <input type="text" value={this.state.randomId} />
      <button onClick={this.generate}>Generate</button>
    </div>;
  }
}