实现上述功能：

下载redux,    npm install redux

新建一个redux文件夹，里面新建一个count_reduce.js和store.js文件

count_reduce.js

export default function count(pre=0,action){let {type,data} =actionconsole.log(action,'action')switch(type){case 'increment':return pre+data;case 'decrement':return pre-data;default :return pre}
}

store.js

// 该文件专门用于暴露一个store对象，整个应用只有一个store对象//引入redux
import { legacy_createStore as createStore } from "redux";
import reducer from './count_reducer'
const store =createStore(reducer)
export default store

页面使用

import React, { Component } from 'react'
import store from '../../redux/store';
export default class index extends Component {//这块主要因为redux不会渲染render,所以在这里监听store值的改变componentDidMount(){store.subscribe(()=>{this.setState({})})}// 相加increment=()=>{let {value} =this.selectVal;store.dispatch({type:'increment',data:value*1})}// 相减decrement=()=>{let {value} =this.selectVal;store.dispatch({type:'decrement',data:value*1})}// 为奇数加加incrementOdd=()=>{let {value} =this.selectVal;let count =store.getState();if(count % 2!==0){store.dispatch({type:'increment',data:value*1})}}// 等一会加加incrementWait=()=>{let {value} =this.selectVal;setTimeout(() => {store.dispatch({type:'increment',data:value*1})}, 500);}render() {return (<div><h2>和为：{store.getState()}</h2><select ref={e=>this.selectVal=e}><option value="1">1</option><option value="2">2</option><option value="3">3</option></select>&nbsp;<button onClick={this.increment}>+</button>&nbsp;<button onClick={this.decrement}>-</button>&nbsp;<button onClick={this.incrementOdd}>和为奇数时再加</button>&nbsp;<button onClick={this.incrementWait}>等一等再加</button>&nbsp;</div>)}
}