手写redux和applyMiddleware中间件react示例

一核心代码

1.reducer

2.store.js

二关于context API的使用

1. MyContext

2. createContext

3. ContextProvider

4. connect

三组件验证效果

1. Todo

2. TodoList

3.TodoItem

4.TodoInput

5. App组件引入Todo组件

一核心代码

1.reducer

// 新增列表数据和改变数组数据
// 将业务逻辑拆分到一个单独文件中，方便进行状态管理
import _ from 'lodash';export interface StateProps {id: number;text: string;isFinished: boolean;}export interface ActionProps {type: string;[key: string]: any;}interface IStateObjectProps {pickerArr: StateProps[];filterTag: 'SHOW_ALL'|'SHOW_FINISHED'|'SHOW_NOT_FINISH';dispatch: any;}
const reducer = (state: IStateObjectProps, action: ActionProps) => {console.log(state, action, 'reducer11111');const pickerArr0 = _.get(state, 'pickerArr')||[];switch (_.get(action, 'type')) {case "ADD":return {...state,pickerArr: [...pickerArr0, _.get(action, 'todo')]};case "CHANGESTATUS":const pickerArr = _.map(pickerArr0, (item) => {if (item.id === action.id) {return Object.assign({}, item, { isFinished: !_.get(item, 'isFinished') });}return item;})||[];return {...state,pickerArr,}case 'SET_VISIBILITY_FILTER': const filterTag = action.filterTag;return {...state,filterTag,};default:return state || {};}};export default reducer

2.store.js

import React from 'react';
import reducer from './reducer'// compose执行顺序就是从后往前
const compose = (...funcs) => {if (funcs.length === 0) return arg => argreturn funcs.reduce((v, cur) => (...args) => (v(cur(...args))))
}function applyMiddleware(...args) {// 将中间件们变成一个数组const middlewares = Array.from({ length: args.length }, (_, _key) => args[_key]);return function (createStore) {return function () {const store = createStore.apply(void 0, arguments);const middlewareAPI = {getState: store.getState,dispatch: store.dispatch,};// map遍历中间件, 执行监听器函数, 形成新数组const chain = middlewares.map((middleware) => middleware(middlewareAPI));// 展开中间件,调整执行顺序,并传入store.dispatchconst dispatch = compose(...chain)(store.dispatch);// 返回需要的存储数据(将dispatch合并进store对象)return {...store,dispatch,};};};
}function legacy_createStore(reducer, preloadedState) {let state = preloadedState || null;const listeners = [];const subscribe = (fn) => listeners.push(fn);const getState = () => state;const dispatch = (action) => {const state1 = reducer(state, action);state = state1// 因为是在获取到最新的state的值之后有执行的监听回调, 所以使用store.subscribe可以监听到最新的state的值!!!listeners.forEach((fn) => fn());return state}return { getState, dispatch, subscribe }
}function createStore(reducer, preloadedState, enhancer) {if (typeof preloadedState === 'function') {return preloadedState(legacy_createStore)(reducer)}if (typeof enhancer === 'function') {return enhancer(legacy_createStore)(reducer, preloadedState)}return legacy_createStore(reducer, preloadedState)
}function createThunkMiddleware(extraArgument) {return ({ dispatch, getState }) => next => action => {if (typeof action === 'function') {return action(dispatch, getState, extraArgument)}return next(action)}
}const thunk = createThunkMiddleware('xxxxxx');
const store = applyMiddleware(thunk)(createStore)(reducer);
// 或者
// const store = createStore(reducer, applyMiddleware(thunk));
// 或者
// const store = createStore(reducer);console.log(store, 'oldState======')
store.subscribe(() => {const newState = store.getState()// 数据可能变化，需要监听最新的console.log(newState, 'newState====');
})export default store;

二关于context API的使用

1. MyContext

import React from "react";const MyContext = React.createContext({});export default MyContext

2. createContext

import React, {ReactNode, memo} from "react";// 已经使用了React.createContext, 这个可以忽略, 只是为了展示createContext功能的简单代码
const createContext = ({}) => {let value = {};const Provider = memo((props: {children: ReactNode;value:{ dispatch: (arg1:any)=>void; getState:() => any;};}) => {value = props.value;return <>{props.children}</>;});const Consumer = memo(({ children }: { children: any }) => {return <>{typeof children === "function" ? children(value) : children}</>;});return { Provider, Consumer };
};export default createContext;

3. ContextProvider

import React, { useState } from "react";
import MyContext from "./MyContext";
import _ from "lodash";
import store from "./store";const useReducer = (state0, dispatch0) => {const [state, dispatch] = useState(state0);const dispatch1 = (action) => {dispatch0(action);dispatch(store.getState());};return [state, dispatch1]
}// 父组件
const ContextProvider = ({ children }) => {const [state, dispatch] = useReducer(store.getState(), store.dispatch);return <MyContext.Provider value={{getState: () => state,dispatch}}>{children}</MyContext.Provider>;
};export default ContextProvider;

4. connect

import React from "react";
import MyContext from "./MyContext";
import _ from "lodash";// 模拟react-redux的 connect高阶函数
const connect = (mapStateToProps, mapDispatchToProps) => {return (Component) => (props) =>wrapper(Component, { mapStateToProps, mapDispatchToProps, ...props });
};const wrapper = (Comp, props) => {const { mapStateToProps, mapDispatchToProps, ...rest } = props;return (<MyContext.Consumer>{(store) => {const dispatchs = mapDispatchToProps(_.get(store, 'dispatch'));let states1 = mapStateToProps(_.get(store, 'getState') ? _.get(store, 'getState')(): {});return <Comp {...{ ...states1, ...dispatchs, ...rest }} />;}}</MyContext.Consumer>);
};export default connect;

三组件验证效果

1. Todo

import React from "react";
import TodoInput from "./TodoInput";
import TodoList from "./TodoList";
import ContextProvider from "./ContextProvider";// 父组件
const Todo = () => {return (<ContextProvider><TodoInput /><TodoList /></ContextProvider>);
};
export default Todo;

2. TodoList

import React, { useEffect } from "react";
import TodoItem from "./TodoItem";
import _ from "lodash";
import connect from "./connect";
import { mapStateTotProps } from "./mapStateToProps";
import { mapDispatchToProps } from "./mapDispatchToProps";
import styles from './TodoList.scss'const TodoList = (props) => {const { todoList } = props;console.log(styles, 'TodoList-styles', props)return (<><p className={styles.title}>checckbox-list: </p><div className="todo-list">{_.map(todoList, (item) => (<TodoItem key={_.get(item, "id")} todo={item || {}} />))}</div><hr /></>);
};export default connect(mapStateTotProps, mapDispatchToProps)(TodoList);

3.TodoItem

import _ from 'lodash';
import React from "react";
import connect from './connect';
import { mapStateTotProps } from "./mapStateToProps";
import { mapDispatchToProps } from "./mapDispatchToProps";// 孙子组件
const TodoItem = (props: any) => {const { todo, changeTodo } = props;// 改变事项状态const handleChange = () => {changeTodo(_.get(todo, 'id'));}return (<div className="todo-item"><input type="checkbox" checked={todo.isFinished} onChange={handleChange} /><span style={{ textDecoration: _.get(todo, 'isFinished') ? 'line-through' : 'none' }}>{todo.text}</span></div>)
}export default connect(mapStateTotProps, mapDispatchToProps)(TodoItem);

4.TodoInput

import React, { useState } from "react";
import connect from './connect';
import { mapStateTotProps } from "./mapStateToProps";
import { mapDispatchToProps } from "./mapDispatchToProps";
import styles from './TodoInput.scss'// 子组件
const TodoInput = (props) => {// console.log(styles, 'styles', props)const [text, setText] = useState("");const {addTodo,showAll,showFinished,showNotFinish,} = props;const handleChangeText = (e: React.ChangeEvent) => {setText((e.target as HTMLInputElement).value);};const handleAddTodo = () => {if (!text) return;addTodo({id: new Date().getTime(),text: text,isFinished: false,});setText("");};return (<div className={styles["todo-input"]}><inputtype="text"placeholder="请输入代办事项"onChange={handleChangeText}value={text}className="aaa"/><button className={styles.btn} onClick={handleAddTodo}>+添加</button><button className={styles.btn} onClick={showAll}>show all</button><button className={styles.btn} onClick={showFinished}>show finished</button><button className={styles.btn} onClick={showNotFinish}>show not finish</button></div>);
};export default connect(mapStateTotProps, mapDispatchToProps)(TodoInput);