.eslintrc.json

{
  "env": {
    "browser": true,
    "es6": true
  },
  "extends": [
    "react-app",
    "react-app/jest",
    "eslint:recommended"
  ],
  "parser": "@babel/eslint-parser",
  "parserOptions": {
    "ecmaFeatures": {
      "experimentalObjectRestSpread": true,
      "jsx": true
    },
    "sourceType": "module",
    "babelOptions": {
      "presets": [
        [ "babel-preset-react-app", false ],
        "babel-preset-react-app/prod"
      ]
    }
  },
  "plugins": [
    "react",
    "jsx-a11y"
  ],
  "rules": {
    // enbale console.log
    "no-console": "off",
    // enable declare variable in if
    "no-cond-assign": "off",
    // enable declare variable width var
    "no-var": "off",
    // enable declare in case
    "no-case-declarations": "off",
    // enable redeclare variable
    "no-redeclare": "off",
    "indent": ["warn", 2, { 
      "SwitchCase": 1,
      "ignoreComments": false
    }],
    "linebreak-style": ["warn", "unix"],
    "quotes": ["warn", "single"],
    "semi": ["warn", "always"],
    "no-unreachable": "warn",
    "no-class-assign": "warn",
    "no-unused-vars": "warn",
    "no-useless-escape": "off",
    "eqeqeq": "off",
    "no-irregular-whitespace": "warn",
    "no-trailing-spaces": "warn",
    "react/jsx-indent": ["warn", 2],
    "eol-last": "error",
    "space-before-function-paren": ["warn", {"named": "never"}],
    "array-bracket-spacing": ["warn", "never"],
    "object-curly-spacing": ["warn", "always"],
    "spaced-comment": "warn",
    "keyword-spacing": ["warn", {"before": true}],
    "space-infix-ops": "error",
    "key-spacing": ["error", { "beforeColon": false }],
    "arrow-spacing": ["error", { "before": true, "after": true }],
    "comma-spacing": ["error", { "before": false, "after": true }],
    "no-duplicate-imports": "error",
    "one-var": ["error", "never"],
    "brace-style": "error",
    "no-multiple-empty-lines": ["error", { "max": 2, "maxEOF": 1 }],
    "no-multi-spaces": "error",
    "react/jsx-closing-tag-location": "error"
  }
}