React17 入门

---

查看 demo

---

ref

{ this.box = box }}>

console.log(this.box); // 获取dom

---

生命周期(针对于组件而言)

Mounting 挂载顺序

1. constructor(props)：初始化 state 和 props 数据
2. componentWillMount() 在组件即将被挂载到页面时执行(16.3已废弃)
3. 新增 static getDerivedStateFromProps(props, state)
4. render()：渲染组件
5. componentDidMount()：在组件被挂载到页面后执行，只在挂载时执行一次

Updation 更新顺序

1. static getDerivedStateFromProps(props, state)
2. shouldComponentUpdate()：在组件被更新之前执行 (return true 更新 , return false 不更新)
3. render()： 渲染页面
4. static getSnapshotBeforeUpdate(prevProps, prevState)
5. componentDidUpdate()：state或props更新后调用

Unmounting 卸载

1. componentWillUnmount() 在组件即将被页面剔除时执行

注意

除了render函数，其他所有的生命周期函数都可以没有

---

CSSTransition 动画库

安装

yarn add react-transition-group

使用

js

import { CSSTransition } from 'react-transition-group';

class TodoList extends Component {
    constructor(props) {
        super(props);
        this.state = {
            show: true,
        };
    }
    render() {
        return (
            

                
                    
hello
                
                提交
            
        );
    }
    toggle() {
        this.setState(() => ({
            show: !this.state.show,
        }));
    }
}

css

.mydemo-enter,
.mydemo-appear {
    opacity: 0;
}

.mydemo-enter-active,
.mydemo-appear-active {
    opacity: 1;
    transition: opacity 1s ease-in;
}

.mydemo-enter-done {
    opacity: 1;
}

.mydemo-exit {
    opacity: 1;
}

.mydemo-exit-active {
    opacity: 0;
    transition: opacity 1s ease-in;
}

.mydemo-exit-done {
    opacity: 0;
}

---

Ant Design UI库

安装

yarn add antd

使用

import { Input, Button, List } from 'antd';
import 'antd/dist/antd.css';


提交

---

Redux

Redux = Reducer + Flux

安装

yarn add redux

原则

1. store是唯一的
2. 只有store能改变自己的内容(store里的数据不是reducer更新的)
3. reducer必须是纯函数

核心API

1. createStore (创建store)
2. store.dispatch(action); (派发action给store)
3. store.getState(); (获取store中所有的数据)
4. store.subscribe (监听store，store发生改变时，自动触发)

具体用法

store/list.js

import store from './store/index';
import { changeInputAction } from './store/actionCreator';

class List extends Component {
    constructor(props) {
        super(props);
        this.state = store.getState();
        store.subscribe(this.storeChange.bind(this)); // store发生改变时，自动触发
    }
    render() {
        return (
            

                
            
        );
    }
    storeChange() {
        this.setState(store.getState());
    }
    change(e) {
        // const action = {
        //     type: 'change_input',
        //     value: e.target.value,
        // };
        const action = changeInputAction(e.target.value);
        store.dispatch(action);
    }
}

export default NewTodoList;

store/actionCreator.js

action的统一管理

export const changeInputAction = value => ({
    type: 'change_input',
    value,
});

store/index.js

import { createStore } from 'redux';
import reducer from './reducer';

const store = createStore(reducer, window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__ && window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__());

export default store;

store/reducer.js

const defaultState = {
    value: ''
};

export default (state = defaultState, action) => {
    console.log(state, action);
    let newState = JSON.parse(JSON.stringify(state)); // 深拷贝,不能直接修改state里的数据
    if (action.type === 'change_input') {
        newState.value = action.value;
    }
    return newState;
};

---

Redux-thunk中间件

Redux-thunk可以使action可以返回函数，从而在store/actionCreator.js中可以进行异步请求(axios)

安装

npm install redux-thunk
或
yarn add redux-thunk

使用

store/index.js

import { createStore, applyMiddleware, compose } from 'redux';
import thunk from 'redux-thunk';
import reducer from './reducer';

// window.__REDUX_DEVTOOLS_EXTENSION__  可使用Redux DevTools插件
const composeEnhancers = window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__ ? window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__({}) : compose;

// 使用Redux-thunk中间件
const enhancer = composeEnhancers(applyMiddleware(thunk));

// 创建store
const store = createStore(reducer, enhancer);

export default store;

TodoList.js

import { Component, Fragment } from 'react';
import { List } from 'antd';
import store from './store/index';
import { getTodoList } from './store/actionCreator';

class TodoList extends Component {
    constructor(props) {
        super(props);
        this.state = store.getState();
        // store.subscribe(this.storeChange.bind(this)); // store发生改变时，自动触发
    }
    render() {
        
              {item} } />
        
    }
    componentDidMount() {
        // 使用redux-thunk后，action可以返回函数，用于进行异步请求(axios)
        const action = getTodoList();
        store.dispatch(action);
    }
}
export default TodoList;

store/actionCreator.js

import axios from 'axios';

export const initListAction = list => ({
    type: 'init_list',
    list,
});

// 使用redux-thunk后，action可以返回函数，用于进行异步请求(axios)
export const getTodoList = () => {
    return dispatch => {
        let list = [];
        axios.get('https://www.fastmock.site/mock/0764b93cba70add273910b232c51aad8/development/api/getHotList').then(function (res) {
            if (res.data.data.length > 0) {
                for (const val of res.data.data) {
                    list.push(val.name);
                }
            }
            const action = initListAction(list);
            dispatch(action); // 将action传给store
        });
    };
};

store/reducer.js

const defaultState = {
    list: []
};

export default (state = defaultState, action) => {
    console.log(state, action);
    let newState = JSON.parse(JSON.stringify(state)); // 深拷贝,不能直接修改state里的数据
    if (action.type === 'init_list') {
        newState.list = action.list;
    }
    return newState;
};

---

Redux-saga中间件

安装

npm install redux-saga --save
或
yarn add redux-saga

使用

1. 创建、使用、运行Redux-saga中间件

src/store/index.js

import { createStore, applyMiddleware, compose } from 'redux';
import thunk from 'redux-thunk';
import createSagaMiddleware from 'redux-saga';
import reducer from './reducer';
import sagas from './sagas'; // 创建sagas.js

// window.__REDUX_DEVTOOLS_EXTENSION__  可使用Redux DevTools插件
const composeEnhancers = window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__ ? window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__({}) : compose;

// 创建Redux-saga中间件
const sagaMiddleware = createSagaMiddleware();

// 使用Redux-thunk中间件、Redux-saga中间件
const enhancer = composeEnhancers(applyMiddleware(thunk, sagaMiddleware));

// 创建store
const store = createStore(reducer, enhancer);

// 运行saga中间件
sagaMiddleware.run(sagas);

export default store;

2. 创建sagas.js

src/store/sagas.js

import { put, takeEvery } from 'redux-saga/effects';
import axios from 'axios';
import { initListAction } from './actionCreator';

// generator 函数
function* mySaga() {
    // 接收 store.dispatch() 传过来的action
    // 接收到get_init_list的action后，会调用getInitList方法
    // getInitList可以执行异步操作
    yield takeEvery('get_init_list', getInitList);
}

function* getInitList() {
    let list = [];
    const res = yield axios.get('https://www.fastmock.site/mock/0764b93cba70add273910b232c51aad8/development/api/getHotList'); // 等待axios请求结束后，直接将结果赋值给res

    if (res.data.data.length > 0) {
        for (const val of res.data.data) {
            list.push(val.name);
        }
    }
    const action = initListAction(list);
    yield put(action);  // 类似于store.dispatch(action);
}

export default mySaga;

3. action的统一管理

src/store/actionCreator.js

export const initListAction = list => ({
    type: 'init_list',
    list,
});

4. Reducer

src/store/reducer.js

const defaultState = {
    list: [],
};

export default (state = defaultState, action) => {
    let newState = JSON.parse(JSON.stringify(state)); // 深拷贝,不能直接修改state里的数据
    if (action.type === 'init_list') {
        newState.list = action.list;
    }
    return newState;
};

5. List.js

import { Component, Fragment } from 'react'; // 占位符
import store from './store/index';
import { List } from 'antd';
import 'antd/dist/antd.css';

class NewTodoList extends Component {
    constructor(props) {
        super(props);
        this.state = store.getState();
        store.subscribe(this.storeChange.bind(this)); // store发生改变时，自动触发
    }
    render() {
        return (
            
                  {item} } />
            
        );
    }
    componentDidMount() {
        const action = {
            type: 'get_init_list',
        };
        store.dispatch(action); // action不仅会被reducer接收，还会被redux-saga接收
    }
    storeChange() {
        this.setState(store.getState());
    }
}

export default NewTodoList;

---

React-redux 第三方模块

安装

npm install react-redux --save
或
yarn add react-redux

使用

Provider组件

provider包裹在根组件外层，使所有的子组件都可以拿到state

1. Provider连接了store
2. Provider内部的所有组件都可以使用store

src/index.js

import React from 'react';
import ReactDOM from 'react-dom';
import { Provider } from 'react-redux';
import './index.css';
import store from './store';
import App from './App';
import reportWebVitals from './reportWebVitals';

ReactDOM.render(
    
        
    ,
    document.getElementById('root')
);

reportWebVitals();

connect连接store

1. mapStateToProps: 把state数据映射到props中,这样在jsx中就可以用this.props.value来代替this.state.value获取值
2. mapDispatchToProps: 把store.disptch()挂载到props上,这样在jsx中就可以用this.props.changeInput来代替store.disptch()改变store里的数据

src/List.js

import { Component, Fragment } from 'react';
import { connect } from 'react-redux';

class List extends Component {
    render() {
        return (
            
                

                    输入内容
                    
                
            
        );
    }
}

// 把state数据映射到props中
// 这样在jsx中就可以用this.props.value来代替this.state.value获取值
const mapStateToProps = state => {
    return {
        value: state.value,
    };
};

// 把store.disptch()挂载到props上
// 这样在jsx中就可以用this.props.changeInput来代替store.disptch()改变store里的数据
const mapDispatchToProps = disptch => {
    return {
        changeInput(e){
            const action = {
                type: 'change_input',
                value: e.target.value,
            };
            disptch(action);
        }
    };
};

export default connect(mapStateToProps, mapDispatchToProps)(List); // List连接store

Reducer

src/store/reducer.js

const defaultState = {
    value: ''
};

export default (state = defaultState, action) => {
    let newState = JSON.parse(JSON.stringify(state)); // 深拷贝,不能直接修改state里的数据
    if (action.type === 'change_input') {
        newState.value = action.value;
    }
    return newState;
};