eslint-plugin-unicorn-x

More than 100 powerful ESLint rules

A modern, faster and lighter fork of eslint-plugin-unicorn.

Install

npm install --save-dev eslint eslint-plugin-unicorn-x

Requires ESLint >=9.20.0 and flat config.

Usage

Use a preset config or configure each rule in eslint.config.js.

If you don't use the preset, ensure you use the same languageOptions config as below.

import eslintPluginUnicorn from 'eslint-plugin-unicorn-x';
import globals from 'globals';

export default [
	{
		languageOptions: {
			globals: globals.builtin,
		},
		plugins: {
			unicorn: eslintPluginUnicorn,
		},
		rules: {
			'unicorn-x/better-regex': 'error',
			'unicorn-x/…': 'error',
		},
	},
	// …
];

Why this fork exists

This fork exists to provide various performance improvements and a reduced install footprint.

Much of this cannot be contributed upstream due to differences in opinion on dependency selection, backwards compatibility requirements, and so on.

We will contribute what we can upstream, and continue to track the original, allowing this plugin to exist as a mostly drop-in replacement to get an easy bump in lint performance.

Migration from eslint-plugin-unicorn

If you are migrating from eslint-plugin-unicorn, simply replace unicorn with unicorn-x in your rules and update the plugin import path:

{
	"rules": {
		// before
		"unicorn/better-regex": "error",

		// after
		"unicorn-x/better-regex": "error",
	}
}

Rules

💼 Configurations enabled in.
✅ Set in the recommended configuration.
🔧 Automatically fixable by the --fix CLI option.
💡 Manually fixable by editor suggestions.

Name	Description	💼	🔧	💡
better-regex	Improve regexes by making them shorter, consistent, and safer.		🔧
catch-error-name	Enforce a specific parameter name in catch clauses.	✅	🔧
consistent-assert	Enforce consistent assertion style with node:assert.	✅	🔧
consistent-date-clone	Prefer passing Date directly to the constructor when cloning.	✅	🔧
consistent-destructuring	Use destructured variables over properties.		🔧	💡
consistent-empty-array-spread	Prefer consistent types when spreading a ternary in an array literal.	✅	🔧
consistent-existence-index-check	Enforce consistent style for element existence checks with indexOf(), lastIndexOf(), findIndex(), and findLastIndex().	✅	🔧
consistent-function-scoping	Move function definitions to the highest possible scope.	✅
custom-error-definition	Enforce correct Error subclassing.		🔧
empty-brace-spaces	Enforce no spaces between braces.	✅	🔧
error-message	Enforce passing a message value when creating a built-in error.	✅
escape-case	Require escape sequences to use uppercase or lowercase values.	✅	🔧
expiring-todo-comments	Add expiration conditions to TODO comments.	✅
explicit-length-check	Enforce explicitly comparing the length or size property of a value.	✅	🔧	💡
filename-case	Enforce a case style for filenames.	✅
import-style	Enforce specific import styles per module.	✅
new-for-builtins	Enforce the use of new for all builtins, except String, Number, Boolean, Symbol and BigInt.	✅	🔧	💡
no-abusive-eslint-disable	Enforce specifying rules to disable in eslint-disable comments.	✅
no-accessor-recursion	Disallow recursive access to this within getters and setters.	✅
no-anonymous-default-export	Disallow anonymous functions and classes as the default export.	✅		💡
no-array-callback-reference	Prevent passing a function reference directly to iterator methods.	✅		💡
no-array-for-each	Prefer for…of over the forEach method.	✅	🔧	💡
no-array-method-this-argument	Disallow using the this argument in array methods.	✅	🔧	💡
no-array-reduce	Disallow Array#reduce() and Array#reduceRight().	✅
no-await-expression-member	Disallow member access from await expression.	✅	🔧
no-await-in-promise-methods	Disallow using await in Promise method parameters.	✅		💡
no-console-spaces	Do not use leading/trailing space between console.log parameters.	✅	🔧
no-document-cookie	Do not use document.cookie directly.	✅
no-empty-file	Disallow empty files.	✅
no-for-loop	Do not use a for loop that can be replaced with a for-of loop.	✅	🔧	💡
no-hex-escape	Enforce the use of Unicode escapes instead of hexadecimal escapes.	✅	🔧
no-instanceof-builtins	Disallow instanceof with built-in objects	✅	🔧	💡
no-invalid-fetch-options	Disallow invalid options in fetch() and new Request().	✅
no-invalid-remove-event-listener	Prevent calling EventTarget#removeEventListener() with the result of an expression.	✅
no-keyword-prefix	Disallow identifiers starting with new or class.
no-lonely-if	Disallow if statements as the only statement in if blocks without else.	✅	🔧
no-magic-array-flat-depth	Disallow a magic number as the depth argument in Array#flat(…).	✅
no-named-default	Disallow named usage of default import and export.	✅	🔧
no-negated-condition	Disallow negated conditions.	✅	🔧
no-negation-in-equality-check	Disallow negated expression in equality check.	✅		💡
no-nested-ternary	Disallow nested ternary expressions.	✅	🔧
no-new-array	Disallow new Array().	✅	🔧	💡
no-new-buffer	Enforce the use of Buffer.from() and Buffer.alloc() instead of the deprecated new Buffer().	✅	🔧	💡
no-null	Disallow the use of the null literal.	✅	🔧	💡
no-object-as-default-parameter	Disallow the use of objects as default parameters.	✅
no-process-exit	Disallow process.exit().	✅
no-single-promise-in-promise-methods	Disallow passing single-element arrays to Promise methods.	✅	🔧	💡
no-static-only-class	Disallow classes that only have static members.	✅	🔧
no-thenable	Disallow then property.	✅
no-this-assignment	Disallow assigning this to a variable.	✅
no-typeof-undefined	Disallow comparing undefined using typeof.	✅	🔧	💡
no-unnecessary-array-flat-depth	Disallow using 1 as the depth argument of Array#flat().	✅	🔧
no-unnecessary-array-splice-count	Disallow using .length or Infinity as the deleteCount or skipCount argument of Array#{splice,toSpliced}().	✅	🔧
no-unnecessary-await	Disallow awaiting non-promise values.	✅	🔧
no-unnecessary-polyfills	Enforce the use of built-in methods instead of unnecessary polyfills.	✅
no-unnecessary-slice-end	Disallow using .length or Infinity as the end argument of {Array,String,TypedArray}#slice().	✅	🔧
no-unreadable-array-destructuring	Disallow unreadable array destructuring.	✅	🔧
no-unreadable-iife	Disallow unreadable IIFEs.	✅
no-unused-properties	Disallow unused object properties.
no-useless-fallback-in-spread	Disallow useless fallback when spreading in object literals.	✅	🔧
no-useless-length-check	Disallow useless array length check.	✅	🔧
no-useless-promise-resolve-reject	Disallow returning/yielding Promise.resolve/reject() in async functions or promise callbacks	✅	🔧
no-useless-spread	Disallow unnecessary spread.	✅	🔧
no-useless-switch-case	Disallow useless case in switch statements.	✅		💡
no-useless-undefined	Disallow useless undefined.	✅	🔧
no-zero-fractions	Disallow number literals with zero fractions or dangling dots.	✅	🔧
number-literal-case	Enforce proper case for numeric literals.	✅	🔧
numeric-separators-style	Enforce the style of numeric separators by correctly grouping digits.	✅	🔧
prefer-add-event-listener	Prefer .addEventListener() and .removeEventListener() over on-functions.	✅	🔧
prefer-array-find	Prefer .find(…) and .findLast(…) over the first or last element from .filter(…).	✅	🔧	💡
prefer-array-flat	Prefer Array#flat() over legacy techniques to flatten arrays.	✅	🔧
prefer-array-flat-map	Prefer .flatMap(…) over .map(…).flat().	✅	🔧
prefer-array-index-of	Prefer Array#{indexOf,lastIndexOf}() over Array#{findIndex,findLastIndex}() when looking for the index of an item.	✅	🔧	💡
prefer-array-some	Prefer .some(…) over .filter(…).length check and .{find,findLast,findIndex,findLastIndex}(…).	✅	🔧	💡
prefer-at	Prefer .at() method for index access and String#charAt().	✅	🔧	💡
prefer-blob-reading-methods	Prefer Blob#arrayBuffer() over FileReader#readAsArrayBuffer(…) and Blob#text() over FileReader#readAsText(…).	✅
prefer-code-point	Prefer String#codePointAt(…) over String#charCodeAt(…) and String.fromCodePoint(…) over String.fromCharCode(…).	✅		💡
prefer-date-now	Prefer Date.now() to get the number of milliseconds since the Unix Epoch.	✅	🔧
prefer-default-parameters	Prefer default parameters over reassignment.	✅	🔧	💡
prefer-dom-node-append	Prefer Node#append() over Node#appendChild().	✅	🔧
prefer-dom-node-dataset	Prefer using .dataset on DOM elements over calling attribute methods.	✅	🔧
prefer-dom-node-remove	Prefer childNode.remove() over parentNode.removeChild(childNode).	✅	🔧	💡
prefer-dom-node-text-content	Prefer .textContent over .innerText.	✅		💡
prefer-event-target	Prefer EventTarget over EventEmitter.	✅
prefer-export-from	Prefer export…from when re-exporting.	✅	🔧	💡
prefer-global-this	Prefer globalThis over window, self, and global.	✅	🔧
prefer-import-meta-properties	Prefer import.meta.{dirname,filename} over legacy techniques for getting file paths.		🔧
prefer-includes	Prefer .includes() over .indexOf(), .lastIndexOf(), and Array#some() when checking for existence or non-existence.	✅	🔧	💡
prefer-json-parse-buffer	Prefer reading a JSON file as a buffer.		🔧
prefer-keyboard-event-key	Prefer KeyboardEvent#key over KeyboardEvent#keyCode.	✅	🔧
prefer-logical-operator-over-ternary	Prefer using a logical operator over a ternary.	✅		💡
prefer-math-min-max	Prefer Math.min() and Math.max() over ternaries for simple comparisons.	✅	🔧
prefer-math-trunc	Enforce the use of Math.trunc instead of bitwise operators.	✅	🔧	💡
prefer-modern-dom-apis	Prefer .before() over .insertBefore(), .replaceWith() over .replaceChild(), prefer one of .before(), .after(), .append() or .prepend() over insertAdjacentText() and insertAdjacentElement().	✅	🔧
prefer-modern-math-apis	Prefer modern Math APIs over legacy patterns.	✅	🔧
prefer-module	Prefer JavaScript modules (ESM) over CommonJS.	✅	🔧	💡
prefer-native-coercion-functions	Prefer using String, Number, BigInt, Boolean, and Symbol directly.	✅	🔧
prefer-negative-index	Prefer negative index over .length - index when possible.	✅	🔧
prefer-node-protocol	Prefer using the node: protocol when importing Node.js builtin modules.	✅	🔧
prefer-number-properties	Prefer Number static properties over global ones.	✅	🔧	💡
prefer-object-from-entries	Prefer using Object.fromEntries(…) to transform a list of key-value pairs into an object.	✅	🔧
prefer-optional-catch-binding	Prefer omitting the catch binding parameter.	✅	🔧
prefer-prototype-methods	Prefer borrowing methods from the prototype instead of the instance.	✅	🔧
prefer-query-selector	Prefer .querySelector() over .getElementById(), .querySelectorAll() over .getElementsByClassName() and .getElementsByTagName() and .getElementsByName().	✅	🔧
prefer-reflect-apply	Prefer Reflect.apply() over Function#apply().	✅	🔧
prefer-regexp-test	Prefer RegExp#test() over String#match() and RegExp#exec().	✅	🔧	💡
prefer-set-has	Prefer Set#has() over Array#includes() when checking for existence or non-existence.	✅	🔧	💡
prefer-set-size	Prefer using Set#size instead of Array#length.	✅	🔧
prefer-single-call	Enforce combining multiple Array#push(), Element#classList.{add,remove}(), and importScripts() into one call.	✅	🔧	💡
prefer-spread	Prefer the spread operator over Array.from(…), Array#concat(…), Array#{slice,toSpliced}() and String#split('').	✅	🔧	💡
prefer-string-raw	Prefer using the String.raw tag to avoid escaping \.	✅	🔧
prefer-string-replace-all	Prefer String#replaceAll() over regex searches with the global flag.	✅	🔧
prefer-string-slice	Prefer String#slice() over String#substr() and String#substring().	✅	🔧
prefer-string-starts-ends-with	Prefer String#startsWith() & String#endsWith() over RegExp#test().	✅	🔧	💡
prefer-string-trim-start-end	Prefer String#trimStart() / String#trimEnd() over String#trimLeft() / String#trimRight().	✅	🔧
prefer-structured-clone	Prefer using structuredClone to create a deep clone.	✅		💡
prefer-switch	Prefer switch over multiple else-if.	✅	🔧
prefer-ternary	Prefer ternary expressions over simple if-else statements.	✅	🔧
prefer-top-level-await	Prefer top-level await over top-level promises and async function calls.	✅		💡
prefer-type-error	Enforce throwing TypeError in type checking conditions.	✅	🔧
prevent-abbreviations	Prevent abbreviations.	✅	🔧
relative-url-style	Enforce consistent relative URL style.	✅	🔧	💡
require-array-join-separator	Enforce using the separator argument with Array#join().	✅	🔧
require-number-to-fixed-digits-argument	Enforce using the digits argument with Number#toFixed().	✅	🔧
require-post-message-target-origin	Enforce using the targetOrigin argument with window.postMessage().			💡
string-content	Enforce better string content.		🔧	💡
switch-case-braces	Enforce consistent brace style for case clauses.	✅	🔧
template-indent	Fix whitespace-insensitive template indentation.	✅	🔧
text-encoding-identifier-case	Enforce consistent case for text encoding identifiers.	✅	🔧	💡
throw-new-error	Require new when creating an error.	✅	🔧

Deleted and deprecated rules

See the list.

Preset configs

See the ESLint docs for more information about extending config files.

Note: Preset configs will also enable the correct language options.

Recommended config

This plugin exports a recommended config that enforces good practices.

import eslintPluginUnicorn from 'eslint-plugin-unicorn-x';

export default [
		// …
		eslintPluginUnicorn.configs.recommended,
		{
			rules: {
				'unicorn-x/better-regex': 'warn',
			},
		},
];

All config

This plugin exports an all that makes use of all rules (except for deprecated ones).

import eslintPluginUnicorn from 'eslint-plugin-unicorn-x';

export default [
		// …
		eslintPluginUnicorn.configs.all,
		{
			rules: {
				'unicorn-x/better-regex': 'warn',
			},
		},
];