访问React中的变量

class MyComponent extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      variableName: 'value'
    };
  }

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

class ParentComponent extends React.Component {
  render() {
    const variableName = 'value';
    return (
      <ChildComponent variableName={variableName} />
    );
  }
}

class ChildComponent extends React.Component {
  render() {
    return (
      <div>{this.props.variableName}</div>
    );
  }
}