import React from 'react';
import ReactDOM from 'react-dom';import './App.css'
class ParentCom extends React.Component {constructor(props) {super(props)this.state = {childData: null}}render() {return ( <div ><h1 > 子元素传递给父级 { this.state.childData } < /h1> <ChildCom setChildData = { this.setChildData }/ > < /div >)}setChildData = (data) => {this.setState({childData: data})}}class ChildCom extends React.Component {constructor(props) {super(props)this.state = {msg: "geyao"}}render() {let sendData = nullreturn ( <div ><button onClick = { this.sendData } > 传递helloworld给父元素 < /button>  <button onClick = {() => { this.props.setChildData('直接调用') } } > 传递helloworld给父元素 < /button> </div >)}sendData = () => {console.log(this.state.msg)console.log(this.props.setChildData(this.state.msg))}}//console.log("这是渲染函数")
ReactDOM.render( < ParentCom / > , document.querySelector("#root"))

运行结果