babel.config.js

module.exports = api => {
    var isTest = api.cache(() => process.env.NODE_ENV === "test")
  
    return {
      ignore: ['node_modules'],
      env: {
        build: {
          ignore: [
            '**/*.d.ts',
            '**/*.test.js',
            '**/*.test.jsx',
            '**/*.test.ts',
            '**/*.test.tsx',
            '__snapshots__',
            '__tests__',
          ],
        },
      },
      presets: [
        ['@babel/preset-env',
          {modules: false,
            targets: {
              browsers: 'Last 2 Chrome versions, Firefox ESR',
              node: '8.9'}}],
        ['@babel/preset-react', {development: process.env.BABEL_ENV !== 'build'}]
      ],
      plugins: [
        '@babel/plugin-proposal-class-properties',
        '@babel/plugin-proposal-object-rest-spread',
        '@babel/plugin-transform-runtime',
        '@babel/plugin-proposal-optional-chaining',
        '@babel/plugin-proposal-nullish-coalescing-operator',
        'babel-plugin-styled-components',
        'react-hot-loader/babel'
      ],
    }
  }