Reactjs 支持实验语法'；classProperties'；isn'；t当前已启用

在Django项目中设置React时，我遇到了这个错误

中的模块构建错误 模块构建失败（来自./node_modules/babel loader/lib/index.js）： 语法错误：C:\Users\1Sun\Cebula3\cebula\u react\assets\js\index.js:Support 对于实验语法，“classProperties”当前未启用（17:9）：

所以，我安装了@babel/plugin建议类属性，并将其放在babelrc中

package.json

{
  "name": "cebula_react",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "start": "webpack-dev-server --config ./webpack.config.js --mode development",
    "test": "echo \"Error: no test specified\" && exit 1",
    "build": "webpack --config prod.config.js"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "babel": {
    "presets": [
      "@babel/preset-env",
      "@babel/preset-react"
    ]
  },
  "devDependencies": {
    "@babel/cli": "^7.0.0",
    "@babel/core": "^7.0.0",
    "@babel/plugin-proposal-class-properties": "^7.0.0",
    "@babel/preset-env": "^7.0.0",
    "@babel/preset-react": "^7.0.0",
    "babel-loader": "^8.0.2",
    "babel-plugin-transform-class-properties": "^6.24.1",
    "react-hot-loader": "^4.3.6",
    "webpack": "^4.17.2",
    "webpack-bundle-tracker": "^0.3.0",
    "webpack-cli": "^3.1.0",
    "webpack-dev-server": "^3.1.8"
  },
  "dependencies": {
    "react": "^16.5.0",
    "react-dom": "^16.5.0"
  }
}

babelrc

{
  "presets": [
    "@babel/preset-env",
    "@babel/preset-react"
  ],
  "plugins": [
    "@babel/plugin-proposal-class-properties"
  ]
}

{
  "presets": [
    [
      "@babel/preset-react",
      { "targets": { "browsers": ["last 3 versions", "safari >= 6"] } }
    ]
  ],
  "plugins": [["@babel/plugin-proposal-class-properties"]]
}

---

但是错误仍然存在，问题是什么？？

更改

"plugins": [
    "@babel/plugin-proposal-class-properties"
  ]

至

"plugins": [
    [
      "@babel/plugin-proposal-class-properties",
      {
        "loose": true
      }
    ]
  ]

这对我很有效

"plugins": [
    "@babel/plugin-proposal-class-properties"
  ]

{
    "presets": [
        "@babel/preset-env",
        "@babel/preset-react"
    ],
    "plugins": [
        [
          "@babel/plugin-proposal-class-properties"
        ]
    ]
}

用上述代码替换.babelrc文件。它为我解决了这个问题。

webpack项目的解决方案 我只是通过将

@babel/plugin提案类属性添加到webpack-config-plugin中来解决这个问题。
我的
webpack.config.js
的模块部分如下所示

module: {
    rules: [
        {
            test: path.join(__dirname, '.'),
            exclude: /(node_modules)/,
            loader: 'babel-loader',
            options: {
                presets: ['@babel/preset-env',
                          '@babel/react',{
                          'plugins': ['@babel/plugin-proposal-class-properties']}]
            }
        }
    ]
}

在对同一个错误进行了近3个小时的搜索并花费时间后，我发现我正在使用名称导入进行React：

import { React } from 'react';

这是完全错误的。只需切换到：

import React from 'react';

所有的错误都消失了。
我希望这对某人有帮助。这是我的。巴别塔LRC：

{
  "presets": [
    "@babel/preset-env",
    "@babel/preset-react"
  ],
  "plugins": [
      "@babel/plugin-proposal-class-properties"
  ]
}

webpack.config.js

const path = require('path');
const devMode = process.env.Node_ENV !== 'production';
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
module.exports = {
  entry: './src/App.js',
  devtool: 'source-map',
  output: {
    path: path.resolve(__dirname, 'public'),
    filename: 'App.js'
  },
  mode: 'development',
  devServer: {
    contentBase: path.resolve(__dirname, 'public'),
    port:9090,
    open: 'google chrome',
    historyApiFallback: true
  },
  module: {
    rules: [
      {
        test: /\.m?js$/,
        exclude: /node_modules/,
        use: {
          loader: 'babel-loader'
        }
      },{
        test: /\.(sa|sc|c)ss$/,
        use: [
          devMode ? 'style-loader' : MiniCssExtractPlugin.loader,
          {
            loader: 'css-loader',
            options: {
              modules: true,
              localIdentName: '[local]--[hash:base64:5]',
              sourceMap: true
            }
          },{
            loader: 'sass-loader'
          }
        ]
      }
    ]
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: devMode ? '[name].css' : '[name].[hash].css',
      chunkFilename: devMode ? '[id].css' : '[id].[hash].css'
    })
  ]
}

package.json

{
  "name": "expense-app",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "build": "webpack",
    "serve": "webpack-dev-server"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "@babel/cli": "^7.1.2",
    "@babel/core": "^7.1.2",
    "@babel/plugin-proposal-class-properties": "^7.1.0",
    "@babel/preset-env": "^7.1.0",
    "@babel/preset-react": "^7.0.0",
    "babel-loader": "^8.0.4",
    "css-loader": "^1.0.0",
    "mini-css-extract-plugin": "^0.4.3",
    "node-sass": "^4.9.3",
    "react-router-dom": "^4.3.1",
    "sass-loader": "^7.1.0",
    "style-loader": "^0.23.1",
    "webpack": "^4.20.2",
    "webpack-cli": "^3.1.2",
    "webpack-dev-server": "^3.1.9"
  },
  "dependencies": {
    "normalize.css": "^8.0.0",
    "react": "^16.5.2",
    "react-dom": "^16.5.2"
  }
}


安装插件建议类属性
npm安装@babel/plugin提案类属性——保存开发

通过添加以下内容更新您的webpack.config.js
'plugins'：['@babel/plugin提案类属性']}]

我发现我的
.babelrc
被忽略的问题，但是我创建了
babel.config.js
，并添加了以下内容：

module.exports = {
  plugins: [
    ['@babel/plugin-proposal-decorators', { legacy: true }],
    ['@babel/plugin-proposal-class-properties', { loose: true }],
    '@babel/plugin-syntax-dynamic-import',
    '@babel/plugin-transform-regenerator',
    [
      '@babel/plugin-transform-runtime',
      {
        helpers: false,
        regenerator: true,
      },
    ],
  ],
  presets: [
    "@babel/preset-flow",
    'module:metro-react-native-babel-preset',
  ],
};

它在React本机应用程序上对我有效，我认为这也将有助于React应用程序。
我正在使用Thread。为了克服这个错误，我必须做以下几点

yarn add @babel/plugin-proposal-class-properties --dev

首先将：@babel/plugin建议类属性安装为开发人员依赖项：

npm install @babel/plugin-proposal-class-properties --save-dev

然后编辑您的.babelrc，使其精确如下：

{
  "presets": [
      "@babel/preset-env",
      "@babel/preset-react"
  ],
  "plugins": [
      [
        "@babel/plugin-proposal-class-properties"
      ]
  ]
}

{
              test: /\.(js|mjs)$/,
              exclude: /@babel(?:\/|\\{1,2})runtime/,
              loader: require.resolve('babel-loader'),
              options: {
                babelrc: false,
                configFile: false,
                compact: false,
                presets: [
                  [
                    require.resolve('babel-preset-react-app/dependencies'),
                    { helpers: true },

                  ],
                  '@babel/preset-env', '@babel/preset-react'
                ],
                plugins: ['@babel/plugin-proposal-class-properties'],
                .
                .
                .

.babelrc文件位于根目录中，package.json位于根目录中

请注意，您应该重新启动webpack dev服务器以使更改生效。
我正在显式使用babel解析器。上述解决方案对我都不起作用。这起作用了

const ast = parser.parse(inputCode, {
      sourceType: 'module',
      plugins: [
        'jsx',
        'classProperties', // '@babel/plugin-proposal-class-properties',
      ],
    });

在
构造函数中移动
状态
对我来说很有效：

。。。
类MyComponent扩展组件{
建造师（男）{
超级（男）
this.state={}
}
}
...

祝你好运…
如果有人在monorepo上工作，那么你需要
配置覆盖
packages/web
中的.js
文件。您需要在该文件中添加
resolveApp（'../../node\u modules/react native ratings'），

我的完整
config override.js文件是

const fs = require('fs');
const path = require('path');
const webpack = require('webpack');

const appDirectory = fs.realpathSync(process.cwd());
const resolveApp = relativePath => path.resolve(appDirectory, relativePath);

// our packages that will now be included in the CRA build step
const appIncludes = [
    resolveApp('src'),
    resolveApp('../components/src'),
    resolveApp('../../node_modules/@react-navigation'),
    resolveApp('../../node_modules/react-navigation'),
    resolveApp('../../node_modules/react-native-gesture-handler'),
    resolveApp('../../node_modules/react-native-reanimated'),
    resolveApp('../../node_modules/react-native-screens'),
    resolveApp('../../node_modules/react-native-ratings'),
    resolveApp('../../node_modules/react-navigation-drawer'),
    resolveApp('../../node_modules/react-navigation-stack'),
    resolveApp('../../node_modules/react-navigation-tabs'),
    resolveApp('../../node_modules/react-native-elements'),
    resolveApp('../../node_modules/react-native-vector-icons'),
];

module.exports = function override(config, env) {
    // allow importing from outside of src folder
    config.resolve.plugins = config.resolve.plugins.filter(
        plugin => plugin.constructor.name !== 'ModuleScopePlugin'
    );
    config.module.rules[0].include = appIncludes;
    config.module.rules[1] = null;
    config.module.rules[2].oneOf[1].include = appIncludes;
    config.module.rules[2].oneOf[1].options.plugins = [
        require.resolve('babel-plugin-react-native-web'),
        require.resolve('@babel/plugin-proposal-class-properties'),
    ].concat(config.module.rules[2].oneOf[1].options.plugins);
    config.module.rules = config.module.rules.filter(Boolean);
    config.plugins.push(
        new webpack.DefinePlugin({ __DEV__: env !== 'production' })
    );

    return config
};

添加

"plugins": [
    [
      "@babel/plugin-proposal-class-properties"
    ]
  ]

进入
。babelrc
对我很有用
 根据GitHub的问题，如果你使用create react应用程序，你应该将你的
.babelrc
或
babel.config.js
配置复制到
webpack.config.js
并删除它们。因为有两行代码
babelrc:false，configFile:false，
你在babelrc中的配置，。。这些都是无用的。
您的
webpack.config.js
位于
/node\u madules/react scripts/config
文件夹中
我这样解决了我的问题：

{
  "presets": [
      "@babel/preset-env",
      "@babel/preset-react"
  ],
  "plugins": [
      [
        "@babel/plugin-proposal-class-properties"
      ]
  ]
}

{
              test: /\.(js|mjs)$/,
              exclude: /@babel(?:\/|\\{1,2})runtime/,
              loader: require.resolve('babel-loader'),
              options: {
                babelrc: false,
                configFile: false,
                compact: false,
                presets: [
                  [
                    require.resolve('babel-preset-react-app/dependencies'),
                    { helpers: true },

                  ],
                  '@babel/preset-env', '@babel/preset-react'
                ],
                plugins: ['@babel/plugin-proposal-class-properties'],
                .
                .
                .

在我的工作环境根目录中，.babelrc文件不存在。然而，package.json中的以下条目解决了这个问题

"babel": {
"presets": [
  "@babel/preset-env",
  "@babel/preset-react"
],
"plugins": [
  "@babel/plugin-proposal-class-properties"
]}

注意：在执行npm或warn命令之前，不要忘记退出控制台并重新打开。
我为src/components->../../components创建了一个符号链接，导致
npm start
发疯并停止将src/components/*.js解释为jsx，从而给出了相同的错误。所有从官方得到的修复指示都是无用的。
当我复制回组件目录时，一切都恢复正常
 
纱线添加--dev@babel/plugin提案类属性

或

npm安装@babel/plugin提案类属性——保存开发
.babelrc
我在尝试用babel传输一些jsx时遇到了同样的问题。下面是对我有效的解决方案。您可以将以下json添加到.babelrc

{
  "presets": [
    "@babel/preset-env",
    "@babel/preset-react"
  ],
  "plugins": [
    "@babel/plugin-proposal-class-properties"
  ]
}

{
  "presets": [
    [
      "@babel/preset-react",
      { "targets": { "browsers": ["last 3 versions", "safari >= 6"] } }
    ]
  ],
  "plugins": [["@babel/plugin-proposal-class-properties"]]
}

对于带有网页包的react项目：

Do:npm安装@babel/插件建议类属性——保存开发
在存在
package.json
和
webpack.config.js
的根文件夹中创建
.babelrc
（如果不存在）文件，并添加以下代码：

{
“预设”：[“@babel/preset env”，“@babel/preset react”]，
“插件”：[
[
“@babel/插件建议类属性”，
{
“松散”：真实
}
]
]
}
用于弹出的create react应用程序项目

我刚刚解决了我的问题，在我的
webpack.config.js
中添加了以下几行：

  presets: [
    [
      require.resolve('babel-preset-react-app/dependencies'),
      { helpers: true },
    ],
    /* INSERT START */
    require.resolve('@babel/preset-env'),
    require.resolve('@babel/preset-react'),
      {
      'plugins': ['@babel/plugin-proposal-class-properties']
    } 
    /* INSERTED END */
  ],

您必须安装

npm install@babel/core@babel/plugin提案类properties@babel/preset env@babel/preset react babel loader

及

更改输入和输出


使用react state有两种方法：

"babel": {
        "presets": [
            "@babel/preset-env",
            "@babel/preset-react"
        ],
        "plugins": [
            "@babel/plugin-proposal-class-properties"
        ]
    }

npm run dev
or
npm run watch

选项1:
只需添加到package.json:

"babel": {
        "presets": [
            "@babel/preset-env",
            "@babel/preset-react"
        ],
        "plugins": [
            "@babel/plugin-proposal-class-properties"
        ]
    }

npm run dev
or
npm run watch

选项2:

"babel": {
        "presets": [
            "@babel/preset-env",
            "@babel/preset-react"
        ],
        "plugins": [
            "@babel/plugin-proposal-class-properties"
        ]
    }

npm run dev
or
npm run watch

1。在根文件夹中创建名为.babelrc的文件。

写入。babelrc:

{ "plugins": ["@babel/plugin-proposal-class-properties"] }

跑步：
npm i@babel/插件提案类属性

3。跑步：

"babel": {
        "presets": [
            "@babel/preset-env",
            "@babel/preset-react"
        ],
        "plugins": [
            "@babel/plugin-proposal-class-properties"
        ]
    }

npm run dev
or
npm run watch

确保您没有错误地从“react router dom/modules/BrowserRouter”导入
import BrowserRouter而不是从“react router dom”导入{BrowserRouter}
您不应该同时拥有/需要
@babel/plugin提案类属性
和
babel plug