Webpack打包警告： We noticed you're using the `useBuiltIns` option without declaring a core-js version._you should also be sure that the version you pass -优快云博客

本文详细解析了在使用Babel和Webpack时遇到的常见错误信息，特别是关于`useBuiltIns`选项的正确配置，避免默认版本变化带来的警告。通过调整`.babelrc`文件中的`corejs`选项，并确保其版本与`package.json`中指定的版本一致，可以有效解决此类问题。

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报错信息

WARNING: We noticed you're using the `useBuiltIns` option without declaring a core-js version. Currently, we assume version 2.x when no version is passed. Since this default version will likely change in future versions of Babel, we recommend explicitly setting the core-js version you are using via the `corejs` option.

You should also be sure that the version you pass to the `corejs` option matches the version specified in your `package.json`'s `dependencies` section. If it doesn't, you need to run one of the following commands:

  npm install --save core-js@2    npm install --save core-js@3
  yarn add core-js@2              yarn add core-js@3


  When setting `useBuiltIns: 'usage'`, polyfills are automatically imported when needed.
  Please remove the `import '@babel/polyfill'` call or use `useBuiltIns: 'entry'` instead.
Hash: a4247c3ebe627bac8fac
Version: webpack 4.31.0
Time: 1286ms
Built at: 2019-05-11 14:18:36
         Asset       Size  Chunks             Chunk Names
    index.html  347 bytes          [emitted]
main.bundle.js   30.4 KiB    main  [emitted]  main
Entrypoint main = main.bundle.js
[./src/index.js] 269 bytes {main} [built]

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解决方式

// .babelrc
{
  "presets": [
    "@babel/preset-flow",
    [
      "@babel/preset-env",
      {
        "targets": {
          "node": "8.10"
        },
        "corejs": "3", // <---  此处加个这个，就没有报错警告了
        "useBuiltIns": "usage"
      }
    ]
  ]
}

其它环境信息

// package.json
{
  "name": "5-4_WebpackDevServer",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "build": "webpack"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "@babel/core": "^7.4.4",
    "@babel/preset-env": "^7.4.4",
    "@babel/preset-react": "^7.0.0",
    "babel-loader": "^8.0.5",
    "clean-webpack-plugin": "^2.0.2",
    "css-loader": "^2.1.1",
    "file-loader": "^3.0.1",
    "html-webpack-plugin": "^3.2.0",
    "node-sass": "^4.12.0",
    "sass-loader": "^7.1.0",
    "style-loader": "^0.23.1",
    "url-loader": "^1.1.2",
    "webpack": "^4.31.0",
    "webpack-cli": "^3.3.2"
  }
}