.babelrc.js

const { NODE_ENV } = process.env
const test = NODE_ENV === 'test'
const loose = true

module.exports = {
  presets: [
    [
      '@babel/preset-env',
      {
        loose,
        ...(test ? { targets: { node: '8' } } : {})
      }
    ],
    '@babel/preset-react',
    '@babel/preset-flow'
  ],
  plugins: [
    '@babel/plugin-transform-flow-strip-types',
    '@babel/plugin-syntax-dynamic-import',
    '@babel/plugin-syntax-import-meta',
    ['@babel/plugin-proposal-class-properties', { loose }],
    '@babel/plugin-proposal-json-strings',
    [
      '@babel/plugin-proposal-decorators',
      {
        legacy: true
      }
    ],
    '@babel/plugin-proposal-function-sent',
    '@babel/plugin-proposal-export-namespace-from',
    '@babel/plugin-proposal-numeric-separator',
    '@babel/plugin-proposal-throw-expressions',
    test && '@babel/plugin-transform-react-jsx-source'
  ].filter(Boolean)
}