.eslintrc

{
    "root": true,
    "parserOptions": {
        "ecmaVersion": 2017,
        "sourceType": "module",
        "ecmaFeatures": {
            "impliedStrict": true
        }
    },
    "env": {
        "browser": true,
        "webextensions": true,
        "es6": true
    },
    "extends": "eslint:recommended",
    "rules": {
        // basic rules
        "semi": 1,
        "semi-style": 2,
        "semi-spacing": 1,
        "camelcase": 2,
        "quotes": ["warn", "double", {
            "avoidEscape": true,
            "allowTemplateLiterals": false
        }],
        "brace-style": 2,
        "keyword-spacing": ["error", {
            "after": true
        }],

        // just to make sure (are defaults)
        "indent": ["error", 4],

        // allow console output for errors in browsers
        "no-console": 0,

        // technically required, because of CSP
        "no-eval": 2,
        "no-implied-eval": 2,

        // great new EcmaScript features
        "prefer-const": ["error", {
            "destructuring": "all"
        }],
        "no-var": 1,
        "prefer-arrow-callback": 1,
        "implicit-arrow-linebreak": 1,
        "arrow-parens": 1,
        "arrow-spacing": 1,
        "no-confusing-arrow": 1,
        "prefer-rest-params": 2,
        "prefer-spread": 2,
        "prefer-template": 1,
        "template-curly-spacing": 1,
        "symbol-description": 2,
        "object-shorthand": ["warn", "consistent-as-needed"],
        "prefer-promise-reject-errors": 2,
        /* "prefer-destructuring": 1, */ // https://github.com/eslint/eslint/issues/10250
        "prefer-numeric-literals": 1,

        // additional rules
        "no-new-object": 2,
        "eqeqeq": ["error", "smart"],
        "curly": ["error", "all"],
        "dot-location": ["error", "property"],
        "dot-notation": 2,
        "no-array-constructor": 2,
        "no-throw-literal": 2,
        "no-self-compare": 2,
        "no-useless-call": 1,
        /* "no-use-before-define": 1, */
        "consistent-return": 2,
        "spaced-comment": 1,
        "no-multi-spaces": 1,
        "no-new-wrappers": 2,
        "no-script-url": 2,
        "no-void": 1,
        "vars-on-top": 1,
        "yoda": ["error", "never"],
        /* "no-warning-comments": 1, */ // should be enabled later
        "require-await": 1,
        "require-jsdoc": ["error", {
            "require": {
                "FunctionDeclaration": true,
                "MethodDefinition": false,
                "ClassDeclaration": false,
                "ArrowFunctionExpression": false
            }
        }],
        "valid-jsdoc": ["error", {
            "prefer": {
                "return": "returns"
            },
            "preferType": {
                "Boolean": "boolean",
                "Number": "number",
                "object": "Object",
                "String": "string",
                "HtmlElement": "HTMLElement"
            },
            "requireReturnType": true,
            "matchDescription": ".+",
            "requireParamDescription": false,
            "requireReturnDescription": false
        }],
        "wrap-iife": ["error", "inside"],
        "no-loop-func": 2,
        "no-unused-expressions": 2,
        // "linebreak-style": 1, // cannot be used when contributing on Windows
    }
}