.babelrc

{
  "presets": [
    ["@babel/preset-env", {
      "useBuiltIns": "usage",
      "corejs": "3",
      "targets": {
        "browsers": [
          "last 5 versions",
          "ie >= 8"
        ]
      }
    }]
  ],
  "plugins": ["@babel/plugin-proposal-class-properties"]
}