babel.config.js

module.exports = function(api) {
  var validEnv = ['development', 'test', 'production']
  var currentEnv = api.env()
  var isDevelopmentEnv = api.env('development')
  var isProductionEnv = api.env('production')
  var isTestEnv = api.env('test')

  if (!validEnv.includes(currentEnv)) {
    throw new Error(
      'Please specify a valid `NODE_ENV` or ' +
      '`BABEL_ENV` environment variables. Valid values are "development", ' +
      '"test", and "production". Instead, received: ' +
      JSON.stringify(currentEnv) +
      '.'
    )
  }

  return {
    presets: [
      isTestEnv && [
        '@babel/preset-env',
        {
          targets: {
            node: 'current'
          }
        }
      ],
      (isProductionEnv || isDevelopmentEnv) && [
        '@babel/preset-env',
        {
          forceAllTransforms: true,
          useBuiltIns: 'usage',
          modules: false,
          exclude: ['transform-typeof-symbol'],
          corejs: {
            version: 3
          }
        }
      ]
    ].filter(Boolean),
    plugins: [
    ].filter(Boolean)
  }
}