Webpack打包警告： We noticed you're u

WARNING (@babel/preset-env): 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

大致错误意思：
您还应该确保传递给“corejs”选项的版本与“包”中指定的版本匹配。json的“依赖性”部分。如果没有，则需要运行以下命令之一，但是运行之后还是运行不起来 查阅的资料解决了

解决方法

// .babelrc
{
presets: [
    [
      '@babel/preset-env',
      {
        targets: '> 1%,last 2 versions,not ie <= 8',
        useBuiltIns: 'entry',
        corejs: '3'//加上他就解决了
      }
    ]
  ],
}