What to do if there is an error when starting the react project

Solution to the error when starting the react project: 1. Enter the project folder, start the project and view the error message; 2. Execute the "npm install" or "npm install react-scripts" command; 3. Execute "npm install @ant-design/pro-field --save" command.

The operating environment of this tutorial: Windows 10 system, react18.0.0 version, Dell G3 computer.

The perfect solution to the error when creating a project in react

1. Preliminary knowledge:

npm (you can also use yarn, this article starts with npm as an example)

npm introduction

• stands for Node Package Manager, which is a package management tool installed along with NodeJS.
• Allow users to download third-party packages written by others from the NPM server for local use.
• Allows users to download and install command line programs written by others from the NPM server for local use.
• Allow users to upload packages or command line programs they write to the NPM server for others to use

npm command

• npm -vTo test whether the installation is successful
• View the installed plug-ins in the current directory:npm list
• Use npm to download the plug-in:npm install [ -g ] [ --save-dev] <name></name>
• Use npm to update the plug-in: npm update [ -g ] [ --save-dev ] <name> </name>

Note:

install can be abbreviated as i, [] means optional, means required

<name> </name>: Package (plug-in library) name

[ -g ]: Global installation. It will be installed in C:\Users\Administrator\AppData\Roaming\npm,and written to the system environment variable; global installation can be called from anywhere through the command line;

non-global Installation: It will be installed in the current location directory;, the local installation will be installed in the node_modules folder of the location directory, and is called by request;

[ --save-dev]: Write The dependencies of package.json need to be published to the production environment, such as react, vue family bucket, ele-ui and other UI frameworks. The plug-ins that must be used when these projects are running need to be placed in dependencies.

##cnpm

Domestic mirror made by Taobao team, Because npm's server is located abroad, the installation may be affected. Taobao mirror installation speed is generally faster.
• Installation: Command prompt execution
• 
  npm install cnpm -g --registry=https://registry.npm.taobao.org
• cnpm -v to test whether the installation is successful

2. Steps to create a project:

1. Global installation: npm install -g create-react-app

2. After switching to the directory where you want to create the project, create a new scaffolding (hello-react): create-react-app hello-react

3. Enter the project folder: cd hello-react

4. Start the project: npm start

Notes:

①After the project is successfully started normally, the following page will appear in the browser

②Open the project folder with vscode and you can see the following files:

③

If you need Expose webpacke configuration (create Do not do anything after completing the project), directly execute the following code: (This operation is irreversible!)

npm run eject

Then enter y, you can see two more folders:

The role of exposed files: for example, introducing antd custom themes on demand

④After installing the scaffolding, you can directly introduce the following packages

//引入react核心组件主库
import React, { Component } from 'react'
//引入ReactDOM 子库
import ReactDOM from 'react-dom'

三、启动项目时可能出现的报错：

1. 'react-app-rewired' 不是内部或外部命令，也不是可运行的程序或批处理文件。

原因：可能是由于create-react-app出现丢包缺陷，手动安装包后，需要重新安装，这样node_modules/.bin/目录下才会重新出现react-scripts的文件，从而解决问题。

解决：npm install 或 npm install react-scripts

（若因为某些原因导致包出故障，就删除node_modules文件夹，重新npm install ）

2.

./src/App.jsx

Module not found: Can't resolve '@ant-design/icons' in 'C:\Users\...

原因：没有安装@ant-design/pro-field

解决：npm install @ant-design/pro-field --save

四、Todolist项目相关库：

npm i prop-types
//对接收的props进行：类型、必要性的限制
import PropTypes from 'prop-types'
npm i nanoid
//生成唯一标识 一般用来充当id或遍历时的index
import {nanoid} from 'nanoid'
id:nanoid()

五、GitHub搜索案例相关库：

npm install pubsub-js --save
//消息订阅-发布机制
import PubSub from 'pubsub-js'
npm install axios
//轻量级ajax请求库
import axios from 'axios'

六、尚硅谷路由案例相关库：

npm install --save react-router-dom
//路由库，前端路由：value是component，用于展示页面内容；
//      后端路由：value是function, 用来处理客户端提交的请求。
import {BrowserRouter,HashRouter,NavLink,Link,Route} from 'react-router-dom'
// V5及之前的版本才有以下三个
import {Switch,Redirect,withRouter} from 'react-router-dom' 
// Switch:懒惰匹配  Redirect：重定向  withRouter：让一般组件具备路由组件所特有的API
 
npm i -save-dev query-string
// 对http请求所带的数据进行解析
import qs from 'querystring'  import qs from 'qs'
// qs.parse() 将字符串解析为对象
// qs.stringify() //将对象解析为字符串（urlencoded编码）

七、UI库案例相关库：

//开源React UI组件库
npm i antd
// 主库
import { Button,DatePicker } from 'antd';
// 子库 图标等
import {WechatOutlined,WeiboOutlined,SearchOutlined} from '@ant-design/icons'
// const 要写在 import后面
const { RangePicker } = DatePicker;
//按需引入 自定义主题步骤：
//1.安装依赖
yarn add react-app-rewired customize-cra babel-plugin-import less less-loader
//2.修改package.json
						"scripts": {
							"start": "react-app-rewired start",
							"build": "react-app-rewired build",
							"test": "react-app-rewired test",
							"eject": "react-scripts eject"
						},
 
//3.根目录下创建config-overrides.js
					const { override, fixBabelImports,addLessLoader} = require('customize-cra');
					module.exports = override(
						fixBabelImports('import', {
							libraryName: 'antd',
							libraryDirectory: 'es',
							style: true,
						}),
						addLessLoader({
							lessOptions:{
								javascriptEnabled: true,
								modifyVars: { '@primary-color': 'green' },
							}
						}),
					);

八、redux相关库：

// 一、基本redux  componnet==>一般组件Count  redux文件==>action、reducer、store.js
npm i redux
 
// redux异步action
npm i redux-thunk
 
// redux中，最为核心的store对象将state、action、reducer联系在一起的对象
// 1.建立store.js文，引入createStore，专门用于创建store对象
//    引入redux-thunk，applyMiddleware，用于支持异步action
import {createStore,applyMiddleware} from 'redux'
import thunk from 'redux-thunk'
 
// 2.引入为Count组件服务的reducer
import countReducer from './count_reducer'
 
// 3. 语法：const store = createStore(reducer)
// store.js文件中一般如下：
export default createStore(countReducer,applyMiddleware(thunk))
 
// 4.store对象的功能
1)store.getState(): 得到state
2)store.dispatch({type:'INCREMENT', number}): 分发action, 触发reducer调用, 产生新的state
3)store.subscribe(render): 注册监听, 当产生了新的state时, 自动调用

// 二、react-redux  容器组件[UI(同名)组件] ： UI组件==>一般组件  containers组件==>外壳
npm i react-redux

//容器组件中，引入connect用于连接UI组件与redux
// Provider让多个组件都可以得到store中state数据
import {connect,Provider} from 'react-redux'
//定义UI组件
class CountUI extends Component{...}
// 使用connect()()创建并暴露一个Count的容器组件
export default connect(mapStateToProps,mapDispatchToProps)(CountUI)
<Count store={store} />
// 给容器组件传递store 连接外部的redux; connect()()用于连接内部的内部的UI组件
 
// 数据共享
 
// store.js汇总所有的reducer变为一个总的reducer
import {combineReducers} from &#39;redux&#39;
const allReducer = combineReducers({
	he:countReducer,
	rens:personReducer
})
// containers组件中：
connect(
	state => ({key:value}), //映射状态 mapStateToProps
           {key:xxxAction} //映射操作状态的方法 mapDispatchToProps
        )(UI组件)
 
 
// redux开发者工具 chrome网上商店中搜索安装 Redux Devtools 工具
npm i redux-devtools-extension
 
import {composeWithDevTools} from &#39;redux-devtools-extension&#39;
export default createStore(reducer,composeWithDevTools(applyMiddleware(thunk)))

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