.babelrc.json

{
  "presets": [["@babel/preset-env", { "targets": { "node": "current" } }]],
  "plugins": ["@babel/plugin-transform-flow-strip-types"],
  "overrides": [
    {
      "exclude": ["**/__tests__/**/*"],
      "presets": ["@babel/preset-env"],
      "plugins": [
        ["@babel/plugin-transform-classes", { "loose": true }],
        ["@babel/plugin-transform-destructuring", { "loose": true }],
        ["@babel/plugin-transform-spread", { "loose": true }],
        ["@babel/plugin-transform-for-of", { "assumeArray": true }]
      ],
      "env": {
        "cjs": {
          "presets": [["@babel/preset-env", { "modules": "commonjs" }]]
        },
        "mjs": {
          "presets": [["@babel/preset-env", { "modules": false }]],
          "plugins": [
            [
              "./resources/add-extension-to-import-paths",
              { "extension": "mjs" }
            ]
          ]
        }
      }
    }
  ]
}