.eslintrc.json

{
  // Modified copy of Drupal's core eslintrc.json'
  "root": true,
  "extends": "eslint:recommended",
  "env": {
    "browser": true,
    "es6": true,
    "node": true
  },
  "globals": {
    "Drupal": true,
    "drupalSettings": true,
    "drupalTranslations": true,
    "jQuery": true,
    "_": true,
    "Cookies": true,
    "Backbone": true,
    "Modernizr": true,
    "Popper": true,
    "Sortable": true,
    "CKEDITOR": true
  },
  "rules": {
    "indent": ["error", 2],
    "consistent-return": ["off"],
    "no-underscore-dangle": ["off"],
    "max-nested-callbacks": ["warn", 5],
    "no-plusplus": ["warn", {
      "allowForLoopAfterthoughts": true
    }],
    "no-param-reassign": ["off"],
    "no-prototype-builtins": ["off"],
    "quotes": ["error", "single", {
      "avoidEscape": true,
      "allowTemplateLiterals": true
      }
    ],
    "valid-jsdoc": ["warn", {
      "prefer": {
        "returns": "return",
        "property": "prop"
      },
      "requireReturn": false
    }],
    "no-unused-vars": ["error"],
    "operator-linebreak": ["error", "after", { "overrides": { "?": "ignore", ":": "ignore" } }]
  }
}