.eslintrc.js

/* eslint-env node */
module.exports = {
	env: {
		es2021: true,
		browser: true
	},
	parserOptions: {
		sourceType: "module"
	},
	extends: "eslint:recommended",
	plugins: ["svelte3"],
	overrides: [
		{
			files: ["*.svelte"],
			processor: "svelte3/svelte3"
		}
	],
	rules: {
		// ADDITIONAL ERROR PREVENTION
		"no-await-in-loop": "warn",
		"no-loss-of-precision": "error",
		"no-promise-executor-return": "error",
		"no-template-curly-in-string": "warn",
		"no-unreachable-loop": "error",
		"no-useless-backreference": "warn",
		"require-atomic-updates": "warn",

		// BEST PRACTICES
		"accessor-pairs": "error",
		"array-callback-return": ["error"],
		"block-scoped-var": "error",
		"class-methods-use-this": "error",
		"consistent-return": "error",
		"curly": ["error", "multi-line", "consistent"],
		"default-case-last": "error",
		"default-param-last": "warn",
		"dot-location": ["error", "property"],
		"dot-notation": "error",
		"eqeqeq": ["error", "always"],
		"max-classes-per-file": "error",
		"guard-for-in": "warn",
		"no-caller": "error",
		"no-constructor-return": "error",
		// "no-else-return": "warn",
		"no-empty-function": "warn",
		// "no-eq-null": "error", // eqeqeq handles this already
		"no-eval": "error",
		"no-extend-native": "error",
		"no-extra-bind": "error",
		"no-extra-label": "error",
		"no-floating-decimal": "error",
		"no-implicit-coercion": "error",
		"no-implicit-globals": "error",
		"no-implied-eval": "error",
		"no-invalid-this": "error",
		"no-iterator": "error",
		"no-labels": "error",
		"no-lone-blocks": "error",
		"no-loop-func": "error",
		"no-multi-spaces": "warn",
		"no-multi-str": "warn",
		"no-new": "error",
		"no-new-func": "error",
		"no-new-wrappers": "error",
		"no-octal-escape": "error",
		"no-param-reassign": "error",
		"no-proto": "error",
		"no-return-assign": "error",
		"no-return-await": "warn",
		"no-script-url": "error",
		"no-self-compare": "error",
		"no-sequences": "error",
		"no-throw-literal": "error",
		"no-unmodified-loop-condition": "warn",
		"no-unused-vars": ["warn", {
			vars: "all", args: "after-used", ignoreRestSiblings: false, argsIgnorePattern: "^_"
		}],
		"no-unused-expressions": ["error", { "allowTernary": true }],
		"no-useless-call": "error",
		"no-useless-concat": "error",
		"no-useless-return": "error",
		"no-void": "error",
		"prefer-promise-reject-errors": "warn",
		"prefer-regex-literals": "error",
		"require-await": "warn",
		// "require-unicode-regexp": "warn",
		"vars-on-top": "error",
		"wrap-iife": ["error", "inside"],
		"yoda": "warn",

		// STRICT MODE
		// "strict": "error",

		// VARIABLES
		"no-label-var": "error",
		"no-undef-init": "warn",
		// "no-undefined": "warn",
		// "no-use-before-define": "error",

		// STYLISTIC ISSUES
		"array-bracket-newline": ["error", "consistent"],
		"array-bracket-spacing": ["error", "never"],
		"array-element-newline": ["error", "consistent"],
		"block-spacing": ["error", "always"],
		"brace-style": ["error", "1tbs"],
		"camelcase": "error",
		"comma-dangle": ["error", "never"],
		"comma-spacing": ["error", { "before": false, "after": true }],
		"comma-style": ["error", "last"],
		"computed-property-spacing": ["error", "never"],
		"eol-last": ["error", "always"],
		"func-call-spacing": ["error", "never"],
		// "func-style": ["warn", "expression"],
		"function-paren-newline": ["error", "multiline-arguments"],
		"implicit-arrow-linebreak": ["error", "beside"],
		"indent": ["error", "tab", { "SwitchCase": 1 }],
		"key-spacing": ["error", { "mode": "minimum" }],
		"keyword-spacing": ["error", { "before": true, "after": true }],
		// "linebreak-style": ["error", "unix"],
		"max-depth": ["warn", 6],
		"max-len": ["warn", { "code": 100, "tabWidth": 2 }],
		"new-cap": ["error", { "newIsCap": true, "capIsNew": true }],
		"new-parens": ["error", "always"],
		// "newline-per-chained-call": ["warn", { "ignoreChainWithDepth": 3 }],
		"no-array-constructor": "error",
		"no-lonely-if": "error",
		"no-mixed-operators": "warn",
		"no-mixed-spaces-and-tabs": ["error", "smart-tabs"],
		"no-multiple-empty-lines": ["warn", { "max": 2, "maxBOF": 0, "maxEOF": 0 }],
		"no-new-object": "error",
		// "no-tabs": ["error", { "allowIndentationTabs": true }],
		"no-trailing-spaces": "error",
		"no-unneeded-ternary": ["error", { "defaultAssignment": false }],
		"no-whitespace-before-property": "error",
		"nonblock-statement-body-position": ["error", "beside"],
		"object-curly-newline": ["error", { "consistent": true }],
		"object-curly-spacing": ["error", "always"],
		"operator-assignment": "warn",
		"operator-linebreak": ["warn", "after", { "overrides": { "?": "before", ":": "before" } }],
		// "padded-blocks": ["warn", "never"],
		"prefer-exponentiation-operator": "error",
		"prefer-object-spread": "error",
		"quotes": ["error", "double", { "avoidEscape": false }],
		"semi": ["error", "always"],
		"semi-spacing": ["error", { "before": false, "after": true }],
		"semi-style": ["error", "last"],
		"space-before-blocks": ["error", "always"],
		"space-before-function-paren": ["error", {
			"anonymous": "always",
			"named": "never",
			"asyncArrow": "always"
		}],
		"space-in-parens": ["error", "never"],
		"space-infix-ops": ["error", { "int32Hint": false }],
		"space-unary-ops": ["error", { "words": true, "nonwords": false }],
		"spaced-comment": ["warn", "always"],
		"switch-colon-spacing": ["error", { "before": false, "after": true }],
		"template-tag-spacing": ["error", "never"],
		"unicode-bom": ["warn", "never"],

		// ECMASCRIPT 6
		"arrow-parens": ["warn", "as-needed"],
		"arrow-spacing": ["error", { "before": true, "after": true }],
		"generator-star-spacing": ["error", { "before": false, "after": true }],
		"no-duplicate-imports": ["error", { "includeExports": true }],
		"no-useless-computed-key": ["error", { "enforceForClassMembers": true }],
		"no-useless-constructor": "error",
		"no-useless-rename": "error",
		"no-var": "error",
		"object-shorthand": ["warn", "always"],
		"prefer-arrow-callback": "warn",
		"prefer-const": "error",
		"prefer-rest-params": "warn",
		"prefer-spread": "warn",
		"rest-spread-spacing": ["error", "never"],
		"template-curly-spacing": ["error", "never"],
		"yield-star-spacing": ["error", { "before": false, "after": true }]
	}
};