一、流程   1、当组件修改数据的时候需要调用store.dispatch传递一个action给store    2、store接受到这个action会将action传递给reducers    3、reducer接受到这个actions后做业务逻辑处理。并返回一个新的newState给store，store这个时候就拥有了state    4、下一次数据再次发生改变的时候就不会使用defaultState 而是用store里面的state    5、需要注意的是 reducers里面必须返回一个纯函数  另外reducers里面的state只允许读不允许修改    6、组件如何监听数据的改变   store.subscribe();监听安装：二、步骤yarn add redux --save-dev1.创建store，对比flux，不需要合并空对象import {createStore, combineReducers} from "redux";import numReducers from "../store/combineReducers/numReducers"import todoReducers from "../store/combineReducers/todoReducers"const reducers = combineReducers({    numReducers,    todoReducers})const store = createStore(reducers);export default store;2.再在store中创建一个reducers.jsreducers必须有一个默认的statereducers必须返回一个纯函数reducers里面的state只允许读，不允许修改,如果修改的话页面是不会发生改变的import reducers from "./reducers"const defaultState = {    inputVal:"",    todoList:[]}export default (state = defaultState,action)=>{    switch(action.type){        case "INPUT_CHANGE":        //深拷贝            const changeState = JSON.parse(JSON.stringify(state))            changeState.inputVal = action.value            return changeState;        case "ADD_ITEM":            const addItemState = JSON.parse(JSON.stringify(state))            addItemState.todoList.push(addItemState.inputVal)            addItemState.inputVal = ""            return addItemState;        case "DEL_ITEM":            const delItemState = JSON.parse(JSON.stringify(state))            delItemState.todoList.splice(action.value,1)            return delItemState    }    return state}3.页面import React,{Component} from "react";import store from "../store"export default class Home extends Component{    constructor(props){        super(props)        this.state = store.getState();        //监听        store.subscribe(this.handleUpdate.bind(this))          }    render(){        let {inputVal,todoList} = this.state        return (            
     
                
                      
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                           {                            todoList.map((item,index)=>{                            return 
       
{item}                                        删除                                    
                        })                    }                
      
            
     
        )    }    handleChange(e){        let val = e.target.value        const action = {                        type:"INPUT_CHANGE",            value:val                   }        store.dispatch(action)    }    handleAdd(){        const action ={            type:"ADD_ITEM"        }        store.dispatch(action)    }    handleDel(params){        const action = {            type:"DEL_ITEM",            value:params        }        store.dispatch(action)    }    handleUpdate(){        this.setState(store.getState())    }}三、通过combineReducers合并多个reducers1.创建combineReducers2.在store>index.js合并import {createStore, combineReducers} from "redux";import numReducers from "../store/combineReducers/numReducers"import todoReducers from "../store/combineReducers/todoReducers"const reducers = combineReducers({    numReducers,    todoReducers})const store = createStore(reducers);export default store;3.state后加入reducers名 render(){        //state后加入reducers名        let {inputVal,todoList} = this.state.todoReducers        return (            
     
                
                      
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