.babelrc

{
  "env": {
    "testing": {
      "presets": [
        ["@babel/preset-env", {
          "targets": {
            "node": "current"
          }
        }],
        "@babel/preset-typescript",
        "power-assert"
      ]
    }
  },
  "presets": [
    [
      "@babel/preset-env",
      {
        "modules": false,
        "targets": {
          "browsers": [
            "last 2 chrome versions",
            "last 2 firefox versions",
          ],
          "node": "6.10"
        }
      }
    ],
    "@babel/preset-typescript"
  ],
  "plugins": [
      "@babel/plugin-proposal-class-properties",
      "@babel/plugin-proposal-object-rest-spread",
      "@babel/plugin-syntax-import-assertions",
      "@babel/plugin-transform-classes",
      "babel-plugin-add-module-exports"
  ]
}