.eslintrc.json

{
  "parser": "@typescript-eslint/parser",
  "plugins": ["@typescript-eslint"],
  "extends": ["eslint:recommended", "next/core-web-vitals", "plugin:@typescript-eslint/recommended"],
  "rules": {
    // Indentation
    "indent": ["error", 2],

    // Semicolons
    "semi": ["error", "always"],

    // Quotes
    "quotes": ["error", "double"],

    // No console.log in production code
    "no-console": "error",

    // Warn about unused variables
    "no-unused-vars": "warn",

    // Disallow undeclared variables
    "no-undef": "error",

    // Disallow unnecessary semicolons
    "no-extra-semi": "error",

    // Enforce return statements in else blocks
    "no-else-return": "error",

    // Disallow implicit type coercion
    "no-implicit-coercion": "error",

    // Disallow multiple consecutive spaces
    "no-multi-spaces": "error",

    // Disallow trailing whitespace
    "no-trailing-spaces": "error",

    // Enforce newline at the end of files
    "eol-last": "error",

    // Disallow trailing commas in objects/arrays
    "comma-dangle": ["error", "never"],

    // Enforce parentheses around arrow function parameters
    "arrow-parens": ["error", "always"],

    // Enforce arrow functions with braces only if needed
    "arrow-body-style": "off",

    // Enforce consistent spacing in object literals
    "object-curly-spacing": ["error", "always"],

    // Allow any spacing in array literals
    "array-bracket-spacing": ["error", "never"],

    // Disallow usage of var
    "no-var": "error",

    // Prefer const over let when variable is not reassigned
    "prefer-const": "error",

    // Prefer template literals over string concatenation
    "prefer-template": "error",

    // Disallow use of variables before they are defined (except functions)
    "no-use-before-define": ["error", { "functions": false }],

    // Disallow variable shadowing in the same scope
    "no-shadow": "error",

    // Disallow specific syntax (ForInStatement, LabeledStatement)
    "no-restricted-syntax": [
      "error",
      {
        "selector": "ForInStatement",
        "message": "for..in loops are discouraged. Use Object.keys() instead."
      },
      {
        "selector": "LabeledStatement",
        "message": "Labels are discouraged in modern code."
      }
    ],

    // Allow underscores in properties
    "no-underscore-dangle": "off",

    // Prefer arrow functions as callbacks
    "prefer-arrow-callback": "error",

    // Prefer rest parameters over arguments
    "prefer-rest-params": "error",

    // Prefer spread operator over apply()
    "prefer-spread": "error",

    // Disallow assignments in return statements
    "no-return-assign": "error"
  },
  "settings": {
    "react": {
      "version": "detect"
    },
    "next": {
      "version": "detect"
    }
  }
}