.eslintrc

{
    "parserOptions": {
        "ecmaVersion": 6,
        "sourceType": "module"
    },
    "env": {
        "browser": true,
        "node": true,
        "es6": true
    },
    "extends": [
        "eslint:recommended"
    ],
    "rules": {
        "semi": ["error", "always"],
        "eqeqeq": ["error", "always"],          // `===`/`!===` instead of `==`/`!=`
        "no-var": "error",                      // `let`/`const` instead of `var`
        "prefer-const": "error",                // `const` instead of `let`

        /* ----- useless code ------ */
        "no-lonely-if": "error",                // `else if` instead of `else { if {`

        /* ------ debug leftovers ----- */
        "no-alert": "error",                    // no `window.alert` or `window.prompt`

        /* ------ shorthand / es6 ----- */
        "no-array-constructor": "error",        // `[1, 2]` instead of `new Array(1, 2)`
        "no-new-object": "error",               // `{}` instead of `new Object()`
        "prefer-rest-params": "error",          // `(...args)` instead of `arguments`
        "prefer-spread": "error",               // `fn(...xs)` instead of `fn.apply(xs)`
        "prefer-arrow-callback": "error",

        /* ----- complexity ----- */
        "max-statements-per-line": "warn",
        "max-statements": ["warn", 100],
        "max-params": ["warn", 8],
        "max-nested-callbacks": ["warn", 4],
        "max-depth": ["warn", 4],
        "max-lines": ["warn", 1000],

        /* ----- stylistic ------ */

        "new-cap": "error",
        "camelcase": "error",
        "brace-style": ["error", "stroustrup"],
        "indent": "error",

        "curly": ["error", "multi"],            // curly braces around multiple statements only
        "block-spacing": "error",
        "dot-notation": "error",                // `x.y` instead of `x["y"]`
        "rest-spread-spacing": ["error", "never"],   // `...xs` instead of `... xs`
        "arrow-spacing": ["error", { "before": true, "after": true }],   // `x => x` instead of `x=>x`
        "space-in-parens": ["error", "never"],
        "object-curly-spacing": ["error", "always"],
    }
}