.eslintrc.json

{
  "root": true,
  "plugins": ["prettier", "@babel/development", "import"],
  "extends": "eslint:recommended",
  "parser": "@babel/eslint-parser",
  "rules": {
    "prettier/prettier": "error"
  },
  "env": { "node": true, "es6": true },
  "overrides": [
    {
      "files": ["**/*.ts"],
      "parser": "@typescript-eslint/parser",
      "plugins": ["@typescript-eslint"],
      "rules": {
        "no-unused-vars": "off",
        "@typescript-eslint/no-unused-vars": "error"
      }
    },
    {
      "files": ["packages/*/src/**/*.{js,ts}"],
      "rules": {
        "@babel/development/no-undefined-identifier": "error",
        "@babel/development/no-deprecated-clone": "error",
        "import/no-extraneous-dependencies": "error",
        "eqeqeq": ["error", "always", { "null": "ignore" }],
        "guard-for-in": "error"
      }
    },
    {
      "files": ["packages/*/test/**/*.js"],
      "env": { "jest": true }
    }
  ]
}