babel.config.js

// * Every now and then, we adopt best practices from CRA
// * https://tinyurl.com/yakv4ggx

// ? https://nodejs.org/en/about/releases
const NODE_OLDEST_LTS = '10.13.0';

module.exports = {
  parserOpts: { strictMode: true },
  plugins: [
    '@babel/plugin-proposal-export-default-from',
    '@babel/plugin-proposal-function-bind',
    '@babel/plugin-transform-typescript'
  ],
  env: {
    // * Used by Jest and `npm test`
    test: {
      sourceMaps: 'both',
      presets: [
        ['@babel/preset-env', { targets: '>1% in US and not ie 11' }],
        ['@babel/preset-typescript', { allowDeclareFields: true }]
        // ? We don't care about minification
      ]
    },
    // * Used by `npm run build`
    production: {
      presets: [
        [
          '@babel/preset-env',
          {
            // ? https://github.com/babel/babel-loader/issues/521#issuecomment-441466991
            //modules: false,
            // ? https://nodejs.org/en/about/releases
            targets: { node: NODE_OLDEST_LTS }
          }
        ],
        ['@babel/preset-typescript', { allowDeclareFields: true }]
        // ? Webpack will handle minification
      ]
    },
    // * Used for compiling ESM code into ./dist/
    esm: {
      presets: [
        [
          '@babel/preset-env',
          {
            // ? https://babeljs.io/docs/en/babel-preset-env#modules
            modules: false,
            // ? https://nodejs.org/en/about/releases
            targets: { node: NODE_OLDEST_LTS }
          }
        ],
        ['@babel/preset-typescript', { allowDeclareFields: true }]
        // ? The end user will handle minification
      ],
      plugins: [
        // ? Interoperable named CJS imports for free
        'babel-plugin-transform-default-named-imports'
      ]
    }
  }
};