当前未启用对实验语法“ classProperties”的支持

时间：2018-09-08 17:46:50

标签： reactjs webpack babeljs babel

当我在Django项目中设置React时，遇到了此错误

ModuleBuildError在             模块构建失败（来自./node_modules/babel-loader/lib/index.js）：     语法错误：C：\ Users \ 1Sun \ Cebula3 \ cebula_react \ assets \ js \ index.js：支持     实验语法“ classProperties”当前未启用（17：9）：

  15 | 
  16 | class BodyPartWrapper extends Component {
> 17 |   state = {
     |         ^
  18 | 
  19 |   }
  20 | 

Add @babel/plugin-proposal-class-properties (https://git.io/vb4SL) to the 
'plugins' section of your Babel config to enable transformation.

因此，我安装了@ babel / plugin-proposal-class-properties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"
  ]
}

但是错误仍然存​​在，这是什么问题？

24 个答案:

答案 0 :(得分：37)

更改 

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

收件人 

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

这对我有用

答案 1 :(得分：20)

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

用上面的代码替换您的.babelrc文件。它为我解决了这个问题。

答案 2 :(得分：16)

Webpack项目解决方案

我只是通过在Webpack配置插件中添加@babel/plugin-proposal-class-properties来解决此问题。 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']}]
            }
        }
    ]
}

答案 3 :(得分：16)

在我的工作环境根目录中，.babelrc文件不存在。但是，在package.json中输入以下内容即可解决此问题。

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

注意：在执行npm或yarn命令之前，请不要忘记退出控制台并重新打开。

答案 4 :(得分：7)

有两种处理反应状态的方法：

选项 1： 只需添加到 package.json：

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

选项 2：

1.在根文件夹中创建一个名为 .babelrc 的文件。

用 .babelrc 编写：

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

npm i @babel/plugin-proposal-class-properties

3.运行：

npm run dev
or
npm run watch

答案 5 :(得分：6)

  • 安装plugin-proposal-class-properties import matplotlib.pyplot as plt # Introduce a column *bin* holding left limits of our bins. df['bin'] = pd.cut(df['volume2'], 50).apply(lambda bin: bin.left) # Group by bins and calculate *f*. g = df[['bin', 'universe']].groupby('bin').sum() # Plot the function using cumulative=True. plt.hist(list(g.index), bins=50, weights=list(g['universe']), cumulative=True) plt.show()

  • 通过添加来更新webpack.config.js npm install @babel/plugin-proposal-class-properties --save-dev

答案 6 :(得分：4)

我刚刚在Laravel Framework 5.7.19上进行了测试，以下步骤有效：

确保.babelrc文件位于应用程序的根文件夹中，并添加以下代码：

Increment

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

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

答案 7 :(得分：4)

经过将近3个小时的搜索并花在相同错误上的时间之后，我发现我正在对React使用名称导入：

import { React } from 'react';

这是完全错误的。只需将其切换为：

import React from 'react';

所有错误都消失了。 我希望这可以帮助别人。这是我的.babelrc：

{
  "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"
  }
}

答案 8 :(得分：3)

首先安装： @ babel / plugin-proposal-class-properties 作为开发依赖项：

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

然后编辑您的.babelrc文件，使其完全像这样：

{
  "presets": [
      "@babel/preset-env",
      "@babel/preset-react"
  ],
  "plugins": [
      [
        "@babel/plugin-proposal-class-properties"
      ]
  ]
}
位于根目录中的

.babelrc 文件，其中 package.json 所在。

请注意，您应该重新启动webpack开发服务器以使更改生效。

答案 9 :(得分：3)

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

或

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

答案 10 :(得分：2)

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 Native应用程序上对我有效，我认为这也将对React应用程序有所帮​​助。

答案 11 :(得分：1)

我在用纱。我必须执行以下操作来克服此错误。

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

答案 12 :(得分：1)

如果某个人在react-native-web-monorepo之后从事monorepo的工作，则需要config-overrides.js到packages/web中归档。您需要在该文件中添加resolveApp('../../node_modules/react-native-ratings'), ...

我完整的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
};

答案 13 :(得分：1)

您必须安装

npm install @babel/core @babel/plugin-proposal-class-properties @babel/preset-env @babel/preset-react babel-loader

和

<块引用>

更改输入和输出

const path = require('path')        
module.exports = {
  entry: path.resolve(__dirname,'src', 'app.js'),
  output: {
    path: path.resolve(__dirname, "public","dist",'javascript'),
    filename: 'bundle.js'
  },
  module: {
    rules: [
      {
        test: /\.(jsx|js)$/,
        exclude: /node_modules/,
        use: [{
          loader: 'babel-loader',
          options: {
            presets: [
              ['@babel/preset-env', {
                "targets": "defaults"
              }],
              '@babel/preset-react'
            ],
            plugins: [
              "@babel/plugin-proposal-class-properties"
            ]
          }
        }]
      }
    ]
  }
}

答案 14 :(得分：1)

在尝试使用babel转换一些jsx时，我遇到了同样的问题。以下是对我有用的解决方案。您可以将以下json添加到您的 .babelrc 

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

答案 15 :(得分：1)

对于使用webpack的react项目：

  1. 执行：npm install @ babel / plugin-proposal-class-properties --save-dev
  2. 在存在.babelrc和package.json的根文件夹中创建webpack.config.js（如果不存在）文件，并在其中添加以下代码：

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

  1. 将以下代码添加到webpack.config.js文件中：

{
            test: /\.jsx?$/,
            exclude: /node_modules/,
            loader: 'babel-loader',
            query: {
                presets: ["@babel/preset-env", "@babel/preset-react"]
            },
            resolve: {
                extensions: ['.js', '.jsx']
            }
}

  1. 关闭终端，然后再次运行npm start。

答案 16 :(得分：0)

确保您没有错误地导入 import BrowserRouter from "react-router-dom/modules/BrowserRouter"; 而不是 import {BrowserRouter} from "react-router-dom";

答案 17 :(得分：0)

用于弹出的create-react-app项目

我刚刚解决了我的案件，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 */
  ],

答案 18 :(得分：0)

尝试了以上所有解决方案，但没有一个起作用。尝试将表添加到类时会出现此问题。

npm我反应本地表组件，然后运行App.js。

./ node_modules / react-native-table-component / components / cell.js 语法错误：C：\ Users \ Dileep \ finaltest \ node_modules \ react-native-table-component \ components \ cell.js：目前未启用对实验语法'classProperties'的支持（5:20）：

将@ babel / plugin-proposal-class-properties（https://git.io/vb4SL）添加到Babel配置的“插件”部分，以启用转换。

答案 19 :(得分：0)

我为src / components创建了一个符号链接-> ../../components，导致npm start陷入困境，并停止将src / components / *。js解释为jsx，从而产生了同样的错误。官方babel对其进行修复的所有说明均无济于事。 当我复制回components目录时，一切都恢复正常！

答案 20 :(得分：0)

根据this GitHub问题，如果您使用create-react-app，则应将.babelrc或babel.config.js配置复制到webpack.config.js并删除它们。由于两个代码行babelrc: false,configFile: false,在babelrc中的配置是无效的。 并且您的webpack.config.js在您的./node_madules/react-scripts/config文件夹中 我这样解决了我的问题：

{
              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'],
                .
                .
                .

答案 21 :(得分：0)

添加

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

进入.babelrc对我有用。

答案 22 :(得分：0)

将state内的constructor function移动对我来说是有效的：

...
class MyComponent extends Component {
  constructor() {
    super()
    this.state = {}
  }
}
...

祝你好运...

答案 23 :(得分：0)

我正在显式使用babel解析器。以上解决方案均不适合我。这行得通。

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