.eslintrc.json

{
    "env": {
      "browser": true,
      "es6": true,
      "node": true
    },
    "extends": "eslint:recommended",
    "parserOptions": {
      "ecmaVersion": 2021,
      "sourceType": "module"
    },
    "rules": {
      // Possible Errors
      "no-console": "warn",
      "no-undef": "error",
      "no-extra-semi": "error",
      "no-dupe-args": "error",
      "no-unreachable": "error",
  
      // Best Practices
      "eqeqeq": ["error", "always"],
      "curly": "error",
      "default-case": "warn",
      "no-alert": "warn",
      "no-else-return": "error",
  
      // Variables
      "no-unused-vars": ["error", { "vars": "all", "args": "after-used" }],
      "no-use-before-define": "error",
      "no-shadow": "warn",
  
      // Stylistic Choices
      "semi": ["error", "always"],
      "quotes": ["error", "single"],
      "indent": ["error", 2],
      "comma-dangle": ["error", "never"],
      "brace-style": ["error", "1tbs"],
      "space-before-function-paren": ["error", "never"],
  
      // ES6
      "no-var": "error",
      "prefer-const": "error",
      "arrow-spacing": ["error", { "before": true, "after": true }],
      "no-duplicate-imports": "error",
  
      // Code Complexity
      "max-depth": ["error", 4],
      "max-lines": ["warn", { "max": 300, "skipBlankLines": true }],
      "complexity": ["error", { "max": 10 }],
  
      // Code Layout
      "newline-per-chained-call": ["error", { "ignoreChainWithDepth": 2 }],
      "eol-last": ["error", "always"],
      "no-trailing-spaces": "error"
    }
  }