<CustomComponent data-id="123" />

class CustomComponent extends React.Component {
  constructor(props) {
    super(props);
    this.customRef = React.createRef();
  }

  render() {
    return <div ref={this.customRef}>Custom Component</div>;
  }
}

class CustomComponent extends React.Component {
  constructor(props) {
    super(props);
    this.customRef = React.createRef();
  }

  componentDidMount() {
    const element = this.customRef.current;
    const dataId = element.getAttribute('data-id');
    console.log(dataId); // 输出：123
  }

  render() {
    return <div ref={this.customRef}>Custom Component</div>;
  }
}