rollup.config.js

import { getBabelOutputPlugin } from '@rollup/plugin-babel'

import path from 'path'
import pkg from './package.json'

function isExternal (candidate) {
  return Object.keys(pkg.dependencies).some(dependency => {
    return candidate.startsWith(dependency)
  })
}

export default [
  {
    input: path.resolve(__dirname, 'src', 'index.js'),
    external: isExternal,
    output: [
      {
        file: pkg.main,
        format: 'cjs',
        sourcemap: true
      },
      {
        file: pkg.module,
        format: 'es',
        sourcemap: true
      }
    ],
    plugins: [
      getBabelOutputPlugin({
        presets: [
          ['@babel/preset-env',
            // {
            //   debug: true,
            //   useBuiltIns: 'usage',
            //   shippedProposals: true,
            //   targets: {
            //     node: '8.10',
            //     edge: '17',
            //     firefox: '60',
            //     chrome: '67',
            //     safari: '11.1'
            //   },
            //   corejs: 3
            // }
          ]
        ],
        plugins: ['@babel/plugin-transform-runtime', '@babel/plugin-proposal-object-rest-spread', '@babel/plugin-proposal-class-properties']
      })
    ]
  }
]