babel.config.js

module.exports = api => {
  api.cache(true);

  return {
    presets: [
      [
        '@babel/env',
        {
          useBuiltIns: 'usage'
        }
      ]
    ],

    plugins: [
      '@babel/proposal-class-properties',
      '@babel/syntax-object-rest-spread',
      process.env.BABEL_ENV !== 'module' && 'add-module-exports',
      [
        'transform-inline-environment-variables',
        { include: ['BABEL_ENV', 'ENV'] }
      ]
    ].filter(Boolean),

    env: {
      test: {
        plugins: ['istanbul']
      },
      development: {
        plugins: [process.env.ENV !== 'browser' && 'source-map-support'].filter(
          Boolean
        )
      },
      module: {
        presets: [['@babel/env', { modules: false }]]
      }
    }
  };
};