为什么我的 css 不能应用于 localhost.3000？

如何解决为什么我的 css 不能应用于 localhost.3000？

我的 INDEX.CSS 无法应用于我的 LOCALHOST.300。我试图安装 CSS 加载器和东西，但它仍然不起作用，有人可以帮助我吗？！ 这是我的 Header.js： 从“反应”导入反应 从 'prop-types' 导入 PropTypes； const 标题 = ({title}) => { 返回 （

            <h1>{title}</h1>
        </header>
            )
        }
        Header.defaultProps ={
          title:'Task Tracker  '  
        }
        Header.propTypes={
            title:PropTypes.string.isRequired,}
// css in js
       // const headingStyle = {
           // color:'red',// backgroundColor:'blue'
       // }
export default Header

这是我的 App.js：

import React from 'react';
import "./index.css"
import Header from "./components/Header";
 function App() {
  return (
<div className="Container">
 <Header  />
</div>
 )
}

export default App

这是我的 index.js：

import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App'; 
import * as reportWebVitals from './reportWebVitals';
require('./index.css');


ReactDOM.render(<React.StrictMode> 
    <App />
    </React.StrictMode>,document.getElementById('root'));

这是我的 index.css：

@import url('https://fonts.googleapis.com/css2?family=Poppins:wght@300;400&display=swap');

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: 'Poppins',sans-serif;
}

.container {
  max-width: 500px;
  margin: 30px auto;
  overflow: auto;
  min-height: 300px;
  border: 1px solid steelblue;
  padding: 30px;
  border-radius: 5px;
}

.header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
}

.btn {
  display: inline-block;
  background: #000;
  color: #fff;
  border: none;
  padding: 10px 20px;
  margin: 5px;
  border-radius: 5px;
  cursor: pointer;
  text-decoration: none;
  font-size: 15px;
  font-family: inherit;
}

.btn:focus {
  outline: none;
}

.btn:active {
  transform: scale(0.98);
}

.btn-block {
  display: block;
  width: 100%;
}

.task {
  background: #f4f4f4;
  margin: 5px;
  padding: 10px 20px;
  cursor: pointer;
}

.task.reminder {
  border-left: 5px solid green;
}

.task h3 {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.add-form {
  margin-bottom: 40px;
}

.form-control {
  margin: 20px 0;
}

.form-control label {
  display: block;
}

.form-control input {
  width: 100%;
  height: 40px;
  margin: 5px;
  padding: 3px 7px;
  font-size: 17px;
}

.form-control-check {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.form-control-check label {
  flex: 1;
}

.form-control-check input {
  flex: 2;
  height: 20px;
}

footer {
  margin-top: 30px;
  text-align: center;
}

我的 4 个文件（index.css、App.js、Header.js 和 index.js）位于我的 src 文件夹内的 components 文件夹中

这是 package.json：

{
  "name": "react-task-number","version": "0.1.0","private": true,"dependencies": {
    "@testing-library/jest-dom": "^5.13.0","@testing-library/react": "^11.2.7","@testing-library/user-event": "^12.8.3","react": "^17.0.2","react-build-dist": "^0.0.8","react-dom": "^17.0.2","react-scripts": "^1.1.5","web-vitals": "^1.1.2"
  },"scripts": {
    "build:dist": "react-build-dist","start": "react-scripts start","build": "react-scripts build","test": "react-scripts test","eject": "react-scripts eject"
  },"eslintConfig": {
    "extends": [
      "react-app","react-app/jest"
    ]
  },"browserslist": {
    "production": [
      ">0.2%","not dead","not op_mini all"
    ],"development": [
      "last 1 chrome version","last 1 firefox version","last 1 safari version"
    ]
  },"devDependencies": {
    "css-loader": "^5.2.6","style-loader": "^0.19.0"
  }
}

这是 webpack.config.js：

const path = require('path');

module.exports = {
  entry: './src/app.js',output: {
    filename: 'App.js',path: path.resolve(__dirname,'dist')
  },module: {
    rules: [
      {
        test: /\.js$/,exclude: /node_modules/,use: {
          loader: 'babel-loader',options: {
            presets: ['@babel/preset-env']
          }
        }
      },// Relevant bit of config for style loader and css loader:
      {
        test: /\.css$/,// the order of `use` is important!
        use: [{ loader: 'style-loader' },{ loader: 'css-loader' }],},]
  },};

这是 webpack.config.prod.js：

const path = require('path');
const merge = require('webpack-merge');
const CleanWebpackPlugin = require('clean-webpack-plugin');
const common = require('./webpack.common.js');

module.exports = merge(common,{
    entry: 'apps/index.js',mode: 'production',devtool: 'source-map',output: {
        path: path.resolve(__dirname,'dist/'),publicPath: '/dist/',filename: 'bundle.js',libraryTarget: 'commonjs2',plugins: [
        new CleanWebpackPlugin(['dist/*.*']),],externals: {
        react: 'react','react-dom': 'react-dom',});

解决方法

因为您在 JSX 中将 'Container' 大写，而您的 css 中的类名是小写