eslint-config/index.js

module.exports = {
  root: true,
  extends: [
    "eslint:recommended",
    "plugin:compat/recommended",
    "plugin:import/recommended",
  ],
  parserOptions: {
    sourceType: "module",
    ecmaVersion: 2018,
    ecmaFeatures: {
      jsx: true,
    },
  },
  rules: {
    // Stylistic:
    "brace-style": "error",
    "camelcase": ["error", {
      properties: "never",
      ignoreDestructuring: true,
    }],
    "comma-dangle": ["error", "always-multiline"],
    "comma-spacing": "error",
    "comma-style": "error",
    "curly": ["error", "all"],
    "func-call-spacing": "error",
    "max-len": ["warn", {
      code: 120,
      tabWidth: 2,
      ignoreComments: false,
      ignoreUrls: true,
      ignoreStrings: true,
      ignoreTemplateLiterals: true,
      ignoreRegExpLiterals: true,
    }],
    "no-multiple-empty-lines": ["error", { max: 1 }],
    "no-tabs": "error",
    "no-trailing-spaces": "error",
    "object-curly-spacing": ["error", "always"],
    "one-var": ["error", {
      var: "never",
      let: "never",
      const: "never",
    }],
    "operator-linebreak": ["error", "after"],
    "padded-blocks": ["error", "never"],
    "quote-props": ["error", "consistent-as-needed"],
    "quotes": ["error", "double", {
      avoidEscape: true,
      allowTemplateLiterals: true,
    }],
    "semi": "error",
    "semi-spacing": "error",
    "space-before-blocks": "error",
    "space-before-function-paren": ["error", {
      named: "never",
      anonymous: "always",
      asyncArrow: "always",
    }],
    "spaced-comment": ["error", "always", {
      line: {
        markers: ["/"],
        exceptions: ["-", "+"],
      },
      block: {
        markers: ["!"],
        exceptions: ["*"],
        balanced: true,
      },
    }],
    "template-tag-spacing": ["error", "never"],

    // ES6:
    "arrow-body-style": ["error", "as-needed", {
      requireReturnForObjectLiteral: false,
    }],
    "arrow-parens": ["error", "always"],
    "arrow-spacing": ["error", { before: true, after: true }],
    "no-confusing-arrow": ["error", { allowParens: true }],
    "no-var": "error",
    "prefer-const": ["error", {
      destructuring: "any",
      ignoreReadBeforeAssign: true,
    }],
    "prefer-destructuring": ["error", {
      VariableDeclarator: {
        array: false,
        object: true,
      },
      AssignmentExpression: {
        array: true,
        object: false,
      },
    }],
    "prefer-rest-params": "error",
    "prefer-spread": "error",
    "template-curly-spacing": "error",
  },
  overrides: [
    {
      // JS-only config
      files: ["*.js"],
      env: {
        es6: true,
      },
      rules: {
        "compat/compat": "error",
      },
    },
    {
      // TypeScript-only config
      files: ["*.ts", "*.tsx", "*.d.ts"],
      extends: [
        "eslint:recommended",
        "plugin:@typescript-eslint/recommended",
        "plugin:@typescript-eslint/recommended-requiring-type-checking",
        "plugin:import/recommended",
        "plugin:import/typescript",
      ],
      plugins: [
        "@typescript-eslint",
      ],
      parser: "@typescript-eslint/parser",
      parserOptions: {
        project: ["./tsconfig.json"],
      },
      rules: {
        // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/restrict-template-expressions.md
        "@typescript-eslint/restrict-template-expressions": "off",
      },
    },
  ],
};