Preset files are not allowed to export objects

问题:

I have a carousel file in which I want to get index.js and build block.build.js so my webpack.config.js is

    //webpack.config.js

var config = {
  entry: './index.js', // Webpack
  output: {
    path: __dirname,
    filename: 'block.build.js',
  },
  devServer: {
    contentBase: './Carousel'
  },
  module : {
    rules : [
      {
        test: /.js$/,
        loader: 'babel-loader',
        exclude: /node_modules/,
        query: {
          presets: ['react', 'es2015'],
          plugins: ['transform-class-properties']
        }
      }
    ]
  }
};
module.exports = config;

The package.json which I use is below :

    {
  "name": "carousel",
  "version": "1.0.0",
  "description": "",
  "main": "webpack.config.js",
  "dependencies": {
    "@babel/core": "^7.0.0-beta.40",
    "babel-cli": "^6.26.0",
    "babel-loader": "^8.0.0-beta.0",
    "babel-plugin-lodash": "^3.3.2",
    "babel-plugin-react-transform": "^3.0.0",
    "babel-preset-react": "^6.24.1",
    "cross-env": "^5.1.3",
    "lodash": "^4.17.5",
    "react": "^16.2.0",
    "react-dom": "^16.2.0",
    "react-swipeable": "^4.2.0",
    "styled-components": "^3.2.1"
  },
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "watch": "webpack --watch",
    "start": "webpack-dev-server --open",
    "build": "webpack"
  },
  "devDependencies": {
    "webpack": "^4.1.1",
    "webpack-cli": "^2.0.10",
    "webpack-dev-server": "^3.1.0"
  },
  "author": "brad traversy",
  "license": "ISC"
}

but I get this error message

ERROR in ./index.js Module build failed: Error: Plugin/Preset files are not allowed to export objects, only functions.

Does anyone know how to solve this ?

回答1:

You're using a combination of Babel 6 and Babel 7. There is no guarantee of compatibility across versions:

"@babel/core": "^7.0.0-beta.40",
"babel-cli": "^6.26.0",
"babel-loader": "^8.0.0-beta.0",
"babel-plugin-lodash": "^3.3.2",
"babel-plugin-react-transform": "^3.0.0",
"babel-preset-react": "^6.24.1",

should be

"@babel/core": "^7.0.0-beta.40",
"@babel/cli": "^7.0.0-beta.40",
"babel-loader": "^8.0.0-beta.0",
"babel-plugin-lodash": "^3.3.2",
"babel-plugin-react-transform": "^3.0.0",
"@babel/preset-react": "^7.0.0-beta.40",

and

    query: {
      presets: ['react', 'es2015'],
      plugins: ['transform-class-properties']
    }

would be

    query: {
      presets: ['@babel/react', '@babel/es2015'],
      plugins: ['@babel/proposal-class-properties']
    }

I'm also confused because you didn't mention @babel/proposal-class-properties in your package.json, but assuming it is in there it should also be updated.

回答2:

It happened to me and a simple solution for me was uninstalling babel-loader@8^ and @babel/core then installed babel-loader@7^

npm uninstall --save babel-loader
npm uninstall --save @babel/core

And then install version 7 babel-loader:-

npm install --save-dev babel-loader@^7

回答3:

Also from babel-loader v8, they have changed a little bit:

webpack 4.x | babel-loader 8.x | babel 7.x

npm install -D babel-loader @babel/core @babel/preset-env webpack

webpack 4.x | babel-loader 7.x | babel 6.x

npm install -D babel-loader@7 babel-core babel-preset-env webpack

(same thing for @babel/preset-react instead of babel-preset-react).

回答4:

Replace your .babelrc file following code this fix my issue

{
  "presets": ["module:metro-react-native-babel-preset"]
}