.babelrc

{
  "presets": [
    ["@babel/preset-env", { "useBuiltIns": "entry", "corejs": { "version": 3, "proposals": true } }],
    "@babel/preset-typescript"
  ],
  "plugins": [
    "@babel/plugin-proposal-class-properties",
    "@babel/plugin-proposal-object-rest-spread",
    "@babel/plugin-transform-runtime",
    "@babel/plugin-proposal-nullish-coalescing-operator",
    "@babel/plugin-proposal-optional-chaining"
  ],
  "env": {
    "node": {
      "plugins": [
        "add-module-exports"
      ]
    },
    "test": {
      "plugins": [
        "add-module-exports",
        "istanbul"
      ]
    }
  }
}