import React, { Component } from 'react';
import './style.css'
class App extends Component {
  constructor(props) {
    super(props);
    this.state = { 
      condition:true // 状态（隐藏或显示）
  // 切换隐藏或显示状态
  toggle=()=>{
    this.setState(()=>({
      condition:this.state.condition?false:true
  render() { 
    return ( 
        {/* 根据状态决定显示或隐藏的类名 */}
        <div className={this.state.condition?'show' :'hide'}>hello</div>
        <button onClick={this.toggle}>切换</button>
export default App;

.show {
  opacity: 1;
  transition: all 1s;
.hide {
  opacity: 0;
  transition: all 1s;