react子組件如何通過父組件傳入的函數，將自己的值再傳回父組件

class Son extends React.Component {
  render() {
    return <input onChange={this.props.onChange}/>;
  }
}

class Father extends React.Component {
  constructor() {
    super();
    this.state = {
      son: ""
    }
  }
  changeHandler(e) {
    this.setState({
      son: e.target.value
    });
  }
  render() {
    return <div>
      <Son onChange={this.changeHandler.bind(this)}/>
      <p>這裏顯示 Son 組件的內容：{this.state.son}</p>
    </div>;
  }
}

ReactDOM.render(<Father/>, mountNode);