2023西安疫情最新消息通知评论优化

目录：

1. react脚手架
2. 创建项目并启动
3. react脚手架项目结构
4. 一个简单的Hello组件
5. 样式的模块化
6. 功能界面的组件化编码流程（通用）
7. 组件的组合使用-TodoList  

1.react脚手架

1. xxx脚手架: 用来帮助程序员快速创建一个基于xxx库的模板项目
   1. 包含了所有需要的配置（语法检查、jsx编译、devServer…）
   2. 下载好了所有相关的依赖
   3. 可以直接运行一个简单效果
2. react提供了一个用于创建react项目的脚手架库: create-react-app
3. 项目的整体技术架构为:  react + webpack + es6 + eslint
4. 使用脚手架开发的项目的特点: 模块化, 组件化, 工程化

2.创建项目并启动

1. 全局安装：npm i -g create-react-app
2. 切换到想创项目的目录，使用命令：create-react-app hello-react
3. 进入项目文件夹：cd hello-react
4. 启动项目：npm start

3.react脚手架项目结构

public ---- 静态资源文件夹

                        favicon.icon ------ 网站页签图标

                        index.html -------- 主页面

                        logo192.png ------- logo图

                        logo512.png ------- logo图

                        manifest.json ----- 应用加壳的配置文件

                        robots.txt -------- 爬虫协议文件

src ---- 源码文件夹

                        App.css -------- App组件的样式

                        App.js --------- App组件

                        App.test.js ---- 用于给App做测试

                        index.css ------ 样式

                        index.js ------- 入口文件

                        logo.svg ------- logo图

                        reportWebVitals.js --- 页面性能分析文件(需要web-vitals库的支持)

                        setupTests.js ---- 组件单元测试的文件(需要jest-dom库的支持)

4.一个简单的Hello组件

Hello.jsx

import React, {Component} from 'react'
import './Hello.css'export default class Hello extends Component {render() {return <h2 className="title">hello,react!</h2>}
}

Hello.css

.title {background-color: orange;
}

Welcome.jsx

import React, {Component} from "react";
import './Welcome.css'export default class Welcome extends Component {render() {return <h2 className="demo">welcome</h2>}
}

Welcome.css

.demo {background-color: skyblue;
}

 App.js

import React from 'react'
import Hello from "./components/Hello/Hello";
import Welcome from "./components/Welcome/Welcome";export default class App extends React.Component {render() {return (<div><Hello></Hello><Welcome></Welcome></div>)}
}

index.js

import React from 'react';
import ReactDOM from 'react-dom/client';
import App from './App';const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(<App/>);

 运行结果：

5.样式的模块化 

Hello.jsx

import React, {Component} from 'react'
import hellocss from './Hello.module.css'export default class Hello extends Component {render() {return <h2 className={hellocss.title}>hello,react!</h2>}
}

Hello.module.css

.title {background-color: orange;
}

 Welcome.jsx

import React, {Component} from "react";
import welcomecss from './Welcome.module.css'export default class Welcome extends Component {render() {return <h2 className={welcomecss.title}>welcome</h2>}
}

Welcome.module.css

.title {background-color: skyblue;
}

 运行结果:

6.功能界面的组件化编码流程（通用）

1. 拆分组件: 拆分界面,抽取组件
2. 实现静态组件: 使用组件实现静态页面效果
3. 实现动态组件
   1. 动态显示初始化数据
      1. 数据类型
      2. 数据名称
      3. 保存在哪个组件?
   2. 交互(从绑定事件监听开始)

7.组件的组合使用-TodoList  

todoList案例相关知识点

1. 拆分组件、实现静态组件，注意: className、style的写法
2. 动态初始化列表，如何确定将数据放在哪个组件的state中?
   1. 某个组件使用放在自身的state中
   2. 某些组件使用:放在他们共同的父组件state中(官方称此操作为:状态提升
3. 关于父子之间通信:
   1. 【父组件】给【子组件】传递数据:通过props传递
   2. 【子组件】给【父组件】传递数据:通过props传递，要求父提前给子传递
4. 注意defaultchecked 和 checked的区别，类似的还有: defaultValue 和 value
5. 状态在哪里，操作状态的方法就在哪里

 Footer.css

/*footer*/
.todo-footer {height: 40px;line-height: 40px;padding-left: 6px;margin-top: 5px;
}.todo-footer label {display: inline-block;margin-right: 20px;cursor: pointer;
}.todo-footer label input {position: relative;top: -1px;vertical-align: middle;margin-right: 5px;
}.todo-footer button {float: right;margin-top: 5px;
}

Footer.jsx

import React, {Component} from 'react';
import './Footer.css'class Footer extends Component {handleCheckAll = (event) => {this.props.checkAllTodo(event.target.checked)}handleClearAllDone = () => {this.props.clearAllDone()}render() {const {todos} = this.propsconst doneCount = todos.reduce((pre, current) => {return pre + (current.done ? 1 : 0)}, 0)const total = todos.lengthreturn (<div className="todo-footer"><label><input type="checkbox" onChange={this.handleCheckAll}checked={doneCount === total && total !== 0 ? true : false}/></label><span><span>已完成{doneCount}</span> / 全部{total}</span><button onClick={this.handleClearAllDone} className="btn btn-danger">清除已完成任务</button></div>);}
}export default Footer;

Header.css

/*header*/
.todo-header input {width: 560px;height: 28px;font-size: 14px;border: 1px solid #ccc;border-radius: 4px;padding: 4px 7px;
}.todo-header input:focus {outline: none;border-color: rgba(82, 168, 236, 0.8);box-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.075), 0 0 8px rgba(82, 168, 236, 0.6);
}

Header.jsx

import React, {Component} from 'react';
import PropTypes from 'prop-types'
import {nanoid} from "nanoid";
import './Header.css'class Header extends Component {static propTypes = {addTodo: PropTypes.func.isRequired}handleKeyUp = (event) => {const {keyCode, target} = eventif (keyCode != 13) returnif (target.value.trim() == '') {alert('输入不能为空')return;}const todoObj = {id: nanoid(), name: target.value, done: false}this.props.addTodo(todoObj)target.value = ''}render() {return (<div className="todo-header"><input onKeyUp={this.handleKeyUp} type="text" placeholder="请输入你的任务名称，按回车键确认"/></div>);}
}export default Header;

Item.css

/*item*/
li {list-style: none;height: 36px;line-height: 36px;padding: 0 5px;border-bottom: 1px solid #ddd;
}li label {float: left;cursor: pointer;
}li label li input {vertical-align: middle;margin-right: 6px;position: relative;top: -1px;
}li button {float: right;display: none;margin-top: 3px;
}li:before {content: initial;
}li:last-child {border-bottom: none;
}

Item.jsx

import React, {Component} from 'react';
import './Item.css'class Item extends Component {state = {mouse: false}handelMouse = (flag) => {return () => {this.setState({mouse: flag})}}handleCheck = (id) => {return (event) => {this.props.updateTodo(id, event.target.checked)}}handleDelete = (id) => {if (window.confirm('确定删除吗？')) {this.props.deleteTodo(id)}}render() {const {id, name, done} = this.propsconst {mouse} = this.statereturn (<li style={{backgroundColor: mouse ? '#ddd' : 'white'}} onMouseEnter={this.handelMouse(true)}onMouseLeave={this.handelMouse(false)}><label><input type="checkbox" checked={done} onChange={this.handleCheck(id)}/><span>{name}</span></label><button onClick={() => {this.handleDelete(id)}}className="btn btn-danger"style={{display: mouse ? 'block' : 'none'}}>删除</button></li>);}
}export default Item;

List.css

/*main*/
.todo-main {margin-left: 0px;border: 1px solid #ddd;border-radius: 2px;padding: 0px;
}.todo-empty {height: 40px;line-height: 40px;border: 1px solid #ddd;border-radius: 2px;padding-left: 5px;margin-top: 10px;
}

List.jsx

import React, {Component} from 'react';
import PropTypes from "prop-types";
import Item from "../Item/Item";
import './List.css'class List extends Component {static propTypes = {todos: PropTypes.array.isRequired,updateTodo: PropTypes.func.isRequired,deleteTodo: PropTypes.func.isRequired}render() {const {todos, updateTodo, deleteTodo} = this.propsreturn (<ul className="todo-main">{todos.map((todo) => {return <Item key={todo.id} {...todo} updateTodo={updateTodo} deleteTodo={deleteTodo}></Item>})}</ul>);}
}export default List;

App.css

/*base*/
body {background: #fff;
}.btn {display: inline-block;padding: 4px 12px;margin-bottom: 0;font-size: 14px;line-height: 20px;text-align: center;vertical-align: middle;cursor: pointer;box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.2), 0 1px 2px rgba(0, 0, 0, 0.05);border-radius: 4px;
}.btn-danger {color: #fff;background-color: #da4f49;border: 1px solid #bd362f;
}.btn-danger:hover {color: #fff;background-color: #bd362f;
}.btn:focus {outline: none;
}.todo-container {width: 600px;margin: 0 auto;
}.todo-container .todo-wrap {padding: 10px;border: 1px solid #ddd;border-radius: 5px;
}

App.js

import React, {Component} from 'react';
import './App.css'
import Header from "./components/Header/Header";
import Footer from "./components/Footer/Footer";
import List from "./components/List/List";class App extends Component {//初始化状态state = {todos: [{id: '001', name: '吃饭', done: true},{id: '002', name: '睡觉', done: true},{id: '003', name: '打代码', done: false},{id: '004', name: '逛街', done: true},]}addTodo = (todoObj) => {const {todos} = this.stateconst newTodos = [todoObj, ...todos]this.setState({todos: newTodos})}updateTodo = (id, done) => {const {todos} = this.stateconst newTodos = todos.map((todoObj) => {if (todoObj.id === id) {return {...todoObj, done: done}} else {return todoObj}})this.setState({todos: newTodos})}deleteTodo = (id) => {const {todos} = this.stateconst newTodos = todos.filter((todoObj) => {return todoObj.id !== id})this.setState({todos: newTodos})}checkAllTodo = (done) => {const {todos} = this.stateconst newTodos = todos.map((todoObj) => {return {...todoObj, done: done}})this.setState({todos: newTodos})}clearAllDone = () => {const {todos} = this.stateconst newTodos = todos.filter((todoObj) => {return !todoObj.done})this.setState({todos: newTodos})}render() {return (<div className="todo-container"><div className="todo-wrap"><Header addTodo={this.addTodo}></Header><List todos={this.state.todos} updateTodo={this.updateTodo} deleteTodo={this.deleteTodo}></List><Footer todos={this.state.todos}checkAllTodo={this.checkAllTodo}clearAllDone={this.clearAllDone}></Footer></div></div>);}
}export default App;

index.js

import React from 'react';
import ReactDOM from 'react-dom/client';
import App from './App';const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(<App/>);

项目结构：

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运行结果：