rollup.config.js

import commonjs from '@rollup/plugin-commonjs';
import babel from '@rollup/plugin-babel';
import pkg from './package.json';

const config = [
  {
    input: 'src/index.js',
    output: {
      file: pkg.browser,
      format: 'esm'
    },
    plugins: [
      commonjs(),
      babel({
        babelHelpers: 'runtime',
        exclude: ['node_modules/**']
      })
    ],
    external (id) {
      return /@babel\/runtime/.test(id) || /mdast-util-to-markdown/.test(id);
    },
  },
  {
    input: 'src/index.js',
    output: [
      {
        file: pkg.main,
        format: 'cjs'
      },
      {
        file: pkg.module,
        format: 'es'
      }
    ],
    plugins: [
      babel({
        babelHelpers: 'runtime',
        exclude: ['node_modules/**']
      })
    ],
    external (id) {
      return /@babel\/runtime/.test(id) || /mdast-util-to-markdown/.test(id);
    },
  }
];

export default config;