.eslintrc.js

module.exports = {
    "root": true,
    "env": {
        "node": true,
        "es6": true
    },

    "parser": "@typescript-eslint/parser",

    "plugins": [
        "mocha",
        "@typescript-eslint"
    ],

    "rules": {
        // syntax preferences
        "quotes": [2, "single", {
            "avoidEscape": true,
            "allowTemplateLiterals": true
        }],
        "semi": 2,
        "no-extra-semi": 2,
        "comma-style": [2, "last"],
        "wrap-iife": [2, "inside"],
        "spaced-comment": [2, "always", {
            "markers": ["*"]
        }],
        "eqeqeq": [2],
        "arrow-body-style": [2, "as-needed"],
        "accessor-pairs": [2, {
            "getWithoutSet": false,
            "setWithoutGet": false
        }],
        "brace-style": [2, "1tbs", {"allowSingleLine": true}],
        "curly": [2, "multi-or-nest", "consistent"],
        "object-curly-spacing": [2, "never"],
        "new-parens": 2,
        "func-call-spacing": 2,
        "arrow-parens": [2, "as-needed"],
        "prefer-const": 2,
        "quote-props": [2, "consistent"],

        // anti-patterns
        "no-var": 2,
        "no-with": 2,
        "no-multi-str": 2,
        "no-caller": 2,
        "no-implied-eval": 2,
        "no-labels": 2,
        "no-new-object": 2,
        "no-octal-escape": 2,
        "no-self-compare": 2,
        "no-shadow-restricted-names": 2,
        "no-cond-assign": 2,
        "no-debugger": 2,
        "no-dupe-keys": 2,
        "no-duplicate-case": 2,
        "no-empty-character-class": 2,
        "no-unreachable": 2,
        "no-unsafe-negation": 2,
        "radix": 2,
        "valid-typeof": 2,
        "no-unused-vars": [2, { "args": "none", "vars": "local", "varsIgnorePattern": "([fx]?describe|[fx]?it|beforeAll|beforeEach|afterAll|afterEach)" }],
        "no-implicit-globals": [2],

        // es2015 features
        "require-yield": 2,
        "template-curly-spacing": [2, "never"],

        // spacing details
        "space-infix-ops": 2,
        "space-in-parens": [2, "never"],
        "space-before-function-paren": [2, "never"],
        "no-whitespace-before-property": 2,
        "keyword-spacing": [2, {
            "overrides": {
                "if": {"after": true},
                "else": {"after": true},
                "for": {"after": true},
                "while": {"after": true},
                "do": {"after": true},
                "switch": {"after": true},
                "return": {"after": true}
            }
        }],
        "arrow-spacing": [2, {
            "after": true,
            "before": true
        }],

        // file whitespace
        "no-multiple-empty-lines": [2, {"max": 2}],
        "no-mixed-spaces-and-tabs": 2,
        "no-trailing-spaces": 2,
        "linebreak-style": [ process.platform === "win32" ? 0 : 2, "unix" ],
        "indent": [2, 2, { "SwitchCase": 1, "CallExpression": {"arguments": 2}, "MemberExpression": 2 }],
        "key-spacing": [2, {
            "beforeColon": false
        }],

        // ensure we don't have any it.only or describe.only in prod
        "mocha/no-exclusive-tests": "error"
    },
    "overrides": [
        {
            "files": ["*.ts"],
            "extends": [
                'plugin:@typescript-eslint/eslint-recommended',
                'plugin:@typescript-eslint/recommended',
            ],
            "rules": {
                "no-unused-vars": 0,
                "@typescript-eslint/no-unused-vars": 2,
                "semi": 0,
                "@typescript-eslint/semi": 2,
                "@typescript-eslint/no-empty-function": 0,
                "@typescript-eslint/no-use-before-define": 0,
                // We know it's bad and use it very sparingly but it's needed :(
                "@typescript-eslint/ban-ts-ignore": 0
            }
        }
    ]
};