1. //下载classnames
    2. yarn add classnames
    1. import React, { Component } from 'react'
    2. import classNames from 'classnames'
    3. import "./index.css"
    4. export default class index extends Component {
    5.     state={
    6.         isflag:false
    7.     }
    8.     changeColor=()=>{
    9.         this.setState((state,props)=>{
    10.             return{
    11.                 isflag:!state.isflag
    12.             }
    13.         })
    14.     }
    15.     render() {
    16.         const {isflag}=this.state
    17.         return (
    18.             <div>
    19.                 <h1 className={classNames("foo",{"hace":isflag})}>我是一个哈哈哈</h1>
    20.                 <button onClick={this.changeColor}>改变颜色</button>
    21.             </div>
    22.         )
    23.     }
    24. }
    1. .hace{
    2.     color: aqua;
    3. }