.eslintrc.json

{
  "extends": [
    "eslint:recommended",
    "plugin:prettier/recommended",
    "prettier/@typescript-eslint"
  ],
  "plugins": [
    "html"
  ],
  "env": {
    "browser": true,
    "commonjs": true,
    "node": true,
    "es6": true,
    "jest": true
  },
  "parserOptions": {
    "ecmaVersion": 2018,
    "sourceType": "module"
  },
  "rules": {
    "no-console": "off",
    "strict": ["error", "global"],
    "curly": "warn",
    "prettier/prettier": "error"
  },
  "parser": "babel-eslint",
  // Taken from create-react-app's eslint configuration
  "overrides": [
    {
      "files": ["**/*.ts?(x)"],
      "parser": "@typescript-eslint/parser",
      "parserOptions": {
        "ecmaVersion": 2018,
        "sourceType": "module",
        "ecmaFeatures": {
          "jsx": true
        },

        // typescript-eslint specific options
        "warnOnUnsupportedTypeScriptVersion": true
      },
      "plugins": ["@typescript-eslint"],
      // If adding a typescript-eslint version of an existing ESLint rule,
      // make sure to disable the ESLint rule here.
      "rules": {
        // TypeScript"s `noFallthroughCasesInSwitch` option is more robust
        "default-case": "off",
        // "tsc" already handles this (https://github.com/typescript-eslint/typescript-eslint/issues/291)
        "no-dupe-class-members": "off",
        // "tsc" already handles this (https://github.com/typescript-eslint/typescript-eslint/issues/477)
        "no-undef": "off",

        // Add TypeScript specific rules (and turn off ESLint equivalents)
        "@typescript-eslint/consistent-type-assertions": "warn",
        "no-array-constructor": "off",
        "@typescript-eslint/no-array-constructor": "warn",
        "no-use-before-define": "off",
        "@typescript-eslint/no-use-before-define": [
          "warn",
          {
            "functions": false,
            "classes": false,
            "variables": false,
            "typedefs": false
          }
        ],
        "no-unused-expressions": "off",
        "@typescript-eslint/no-unused-expressions": [
          "error",
          {
            "allowShortCircuit": true,
            "allowTernary": true,
            "allowTaggedTemplates": true
          }
        ],
        "no-unused-vars": "off",
        "@typescript-eslint/no-unused-vars": [
          "warn",
          {
            "args": "none",
            "ignoreRestSiblings": true
          }
        ],
        "no-useless-constructor": "off",
        "@typescript-eslint/no-useless-constructor": "warn"
      }
    }
  ]
}