.babelrc

{
  "env": {
    "production": {
      "presets": [
        [
          "@babel/preset-env",
          {
            "modules": false
          }
        ]
      ],
      "plugins": [
        "@babel/plugin-proposal-class-properties"
      ]
    },
    "test": {
      "presets": [
        "@babel/preset-env"
      ],
      "plugins": [
        "@babel/plugin-proposal-class-properties"
      ]  
    }
  }
}