eslint-plugin-unicorn

eslint-plugin-unicorn

More than 300 powerful ESLint rules

Most rules target JavaScript and TypeScript, but some also lint CSS, HTML, JSON, and Markdown when used with the matching ESLint language plugin.

Propose a new rule

We do not accept pull requests because of too much AI slop.

Install

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

Requires ESLint >=10.4, flat config, and ESM.

You might want to check out XO, which includes this plugin.

Usage

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

If you don't use a preset, set the same languageOptions as shown below.

import unicorn from 'eslint-plugin-unicorn';
import {defineConfig} from 'eslint/config';
import globals from 'globals';

export default defineConfig([
	{
		files: ['**/*.js'],
		languageOptions: {
			globals: globals.builtin,
		},
		plugins: {
			unicorn,
		},
		rules: {
			'unicorn/prefer-module': 'error',
			'unicorn/…': 'error',
		},
	},
	// …
]);

For TypeScript, scope Unicorn to TypeScript files and configure a TypeScript parser for the same config object:

import typescriptEslintParser from '@typescript-eslint/parser';
import unicorn from 'eslint-plugin-unicorn';
import {defineConfig} from 'eslint/config';
import globals from 'globals';

export default defineConfig([
	{
		files: ['**/*.ts'],
		languageOptions: {
			globals: globals.builtin,
			parser: typescriptEslintParser,
		},
		plugins: {
			unicorn,
		},
		rules: {
			'unicorn/prefer-module': 'error',
			'unicorn/…': 'error',
		},
	},
	// …
]);

Rules

Configurations enabled in.
Set in the recommended configuration.
Set in the unopinionated configuration.
Automatically fixable by the --fix CLI option.
Manually fixable by editor suggestions.
Requires type information.

Name	Description
better-dom-traversing	Prefer better DOM traversal APIs.
catch-error-name	Enforce a specific parameter name in catch clauses.
class-reference-in-static-methods	Enforce consistent class references in static methods.
comment-content	Enforce better comment content.
consistent-assert	Enforce consistent assertion style with node:assert.
consistent-boolean-name	Enforce consistent naming for boolean names.
consistent-class-member-order	Enforce consistent class member order.
consistent-compound-words	Enforce consistent spelling of compound words in identifiers.
consistent-conditional-object-spread	Enforce consistent conditional object spread style.
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-export-decorator-position	Enforce consistent decorator position on exported classes.
consistent-function-scoping	Move function definitions to the highest possible scope.
consistent-function-style	Enforce function syntax by role.
consistent-json-file-read	Enforce consistent JSON file reads before JSON.parse().
consistent-optional-chaining	Enforce consistent optional chaining for same-base member access.
consistent-template-literal-escape	Enforce consistent style for escaping ${ in template literals.
consistent-tuple-labels	Enforce consistent labels on tuple type elements.
custom-error-definition	Enforce correct Error subclassing.
default-export-style	Enforce consistent default export declarations.
dom-node-dataset	Enforce consistent style for DOM element dataset access.
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.
explicit-timer-delay	Enforce or disallow explicit delay argument for setTimeout() and setInterval().
filename-case	Enforce a case style for filenames and directory names.
id-match	Require identifiers to match a specified regular expression.
import-style	Enforce specific import styles per module.
isolated-functions	Prevent usage of variables from outside the scope of isolated functions.
logical-assignment-operators	Require or disallow logical assignment operator shorthand
max-nested-calls	Limit the depth of nested calls.
name-replacements	Enforce replacements for variable, property, and filenames.
new-for-builtins	Enforce correct use of new for builtin constructors.
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-accidental-bitwise-operator	Disallow bitwise operators where a logical operator was likely intended.
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-concat-in-loop	Disallow array accumulation with Array#concat() in loops.
no-array-fill-with-reference-type	Disallow using reference values as Array#fill() values.
no-array-from-fill	Disallow .fill() after Array.from({length: …}).
no-array-front-mutation	Disallow front-of-array mutation.
no-array-method-this-argument	Disallow using the this argument in array methods.
no-array-reduce	Disallow Array#reduce() and Array#reduceRight().
no-array-reverse	Prefer Array#toReversed() over Array#reverse().
no-array-sort	Prefer Array#toSorted() over Array#sort().
no-array-sort-for-min-max	Disallow sorting arrays to get the minimum or maximum value.
no-array-splice	Prefer Array#toSpliced() over Array#splice().
no-asterisk-prefix-in-documentation-comments	Disallow asterisk prefixes in documentation comments.
no-async-promise-finally	Disallow async functions as Promise#finally() callbacks.
no-await-expression-member	Disallow member access from await expression.
no-await-in-promise-methods	Disallow using await in Promise method parameters.
no-blob-to-file	Disallow unnecessary Blob to File conversion.
no-boolean-sort-comparator	Disallow boolean-returning sort comparators.
no-break-in-nested-loop	Disallow break and continue in nested loops and switches inside loops.
no-canvas-to-image	Prefer drawing canvases directly instead of converting them to images.
no-chained-comparison	Disallow chained comparisons such as a < b < c.
no-collection-bracket-access	Disallow accessing Map, Set, WeakMap, and WeakSet entries with bracket notation.
no-computed-property-existence-check	Disallow dynamic object property existence checks.
no-confusing-array-splice	Disallow confusing uses of Array#{splice,toSpliced}().
no-confusing-array-with	Disallow confusing uses of Array#with().
no-console-spaces	Do not use leading/trailing space between console.log parameters.
no-constant-zero-expression	Disallow arithmetic and bitwise operations that always evaluate to 0.
no-declarations-before-early-exit	Disallow declarations before conditional early exits when they are only used after the exit.
no-document-cookie	Do not use document.cookie directly.
no-double-comparison	Disallow two comparisons of the same operands that can be combined into one.
no-duplicate-if-branches	Disallow duplicate adjacent branches in if chains.
no-duplicate-logical-operands	Disallow adjacent duplicate operands in logical expressions.
no-duplicate-loops	Disallow .map() and .filter() in for…of and for await…of loop headers.
no-duplicate-set-values	Disallow duplicate values in Set constructor array literals.
no-empty-file	Disallow empty files.
no-error-property-assignment	Disallow assigning to built-in error properties.
no-exports-in-scripts	Disallow exports in scripts.
no-for-each	Prefer for…of over the forEach method.
no-for-loop	Do not use a for loop that can be replaced with a for-of loop.
no-global-object-property-assignment	Disallow assigning properties on the global object.
no-immediate-mutation	Disallow immediate mutation after variable assignment.
no-impossible-length-comparison	Disallow impossible comparisons against .length or .size.
no-incorrect-query-selector	Disallow incorrect querySelector() and querySelectorAll() usage.
no-incorrect-template-string-interpolation	Disallow incorrect template literal interpolation syntax.
no-instanceof-builtins	Disallow instanceof with built-in objects
no-invalid-argument-count	Disallow calling functions and constructors with an invalid number of arguments.
no-invalid-character-comparison	Disallow comparing a single character from a string to a multi-character string.
no-invalid-fetch-options	Disallow invalid options in fetch() and new Request().
no-invalid-file-input-accept	Disallow invalid accept values on file inputs.
no-invalid-remove-event-listener	Prevent calling EventTarget#removeEventListener() with the result of an expression.
no-invalid-well-known-symbol-methods	Disallow invalid implementations of well-known symbol methods.
no-keyword-prefix	Disallow identifiers starting with new or class.
no-late-current-target-access	Disallow accessing event.currentTarget after the synchronous event dispatch has finished.
no-late-event-control	Disallow event-control method calls after the synchronous event dispatch has finished.
no-lonely-if	Disallow if statements as the only statement in if blocks without else.
no-loop-iterable-mutation	Disallow mutating a loop iterable during iteration.
no-magic-array-flat-depth	Disallow a magic number as the depth argument in Array#flat(…).
no-manually-wrapped-comments	Disallow manually wrapped comments.
no-mismatched-map-key	Disallow checking a Map key before accessing a different key.
no-misrefactored-assignment	Disallow misrefactored compound assignments where the target is duplicated in the right-hand side.
no-named-default	Disallow named usage of default import and export.
no-negated-array-predicate	Disallow negated array predicate calls.
no-negated-comparison	Disallow negated comparisons.
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-non-function-verb-prefix	Disallow non-function values with function-style verb prefixes.
no-nonstandard-builtin-properties	Disallow non-standard properties on built-in objects.
no-null	Disallow the use of the null literal.
no-object-as-default-parameter	Disallow the use of objects as default parameters.
no-object-methods-with-collections	Disallow Object methods with Map or Set.
no-optional-chaining-on-undeclared-variable	Disallow optional chaining on undeclared variables.
no-process-exit	Disallow process.exit().
no-redundant-comparison	Disallow comparisons made redundant by an equality check in the same logical AND.
no-return-array-push	Disallow using the return value of Array#push() and Array#unshift().
no-selector-as-dom-name	Disallow selector syntax in DOM names.
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-subtraction-comparison	Prefer comparing values directly over subtracting and comparing to 0.
no-thenable	Disallow then property.
no-this-assignment	Disallow assigning this to a variable.
no-this-outside-of-class	Disallow this outside of classes.
no-top-level-assignment-in-function	Disallow assigning to top-level variables from inside functions.
no-top-level-side-effects	Disallow top-level side effects in exported modules.
no-typeof-undefined	Disallow comparing undefined using typeof.
no-uncalled-method	Disallow referencing methods without calling them.
no-undeclared-class-members	Require class members to be declared.
no-unnecessary-array-flat-depth	Disallow using 1 as the depth argument of Array#flat().
no-unnecessary-array-flat-map	Disallow Array#flatMap() callbacks that only wrap a single item.
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-boolean-comparison	Disallow unnecessary comparisons against boolean literals.
no-unnecessary-fetch-options	Disallow unnecessary options in fetch() and new Request().
no-unnecessary-global-this	Disallow unnecessary globalThis references.
no-unnecessary-nested-ternary	Disallow unnecessary nested ternary expressions.
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-unnecessary-splice	Disallow Array#splice() when simpler alternatives exist.
no-unreadable-array-destructuring	Disallow unreadable array destructuring.
no-unreadable-for-of-expression	Disallow unreadable iterable expressions in for…of and for await…of loop headers.
no-unreadable-iife	Disallow unreadable IIFEs.
no-unreadable-new-expression	Disallow unreadable new expressions.
no-unreadable-object-destructuring	Disallow unreadable object destructuring.
no-unsafe-buffer-conversion	Prevent unsafe use of ArrayBuffer view .buffer.
no-unsafe-dom-html	Disallow unsafe DOM HTML APIs.
no-unsafe-promise-all-settled-values	Disallow reading .value from Promise.allSettled() results without a fulfilled status guard.
no-unsafe-property-key	Disallow unsafe values as property keys.
no-unsafe-string-replacement	Disallow non-literal replacement values in String#replace() and String#replaceAll().
no-unused-array-method-return	Disallow ignoring the return value of selected array methods.
no-unused-properties	Disallow unused object properties.
no-useless-boolean-cast	Disallow unnecessary Boolean() casts in array predicate callbacks.
no-useless-coercion	Disallow useless type coercions of values that are already of the target type.
no-useless-collection-argument	Disallow useless values or fallbacks in Set, Map, WeakSet, or WeakMap.
no-useless-compound-assignment	Disallow useless compound assignments such as x += 0.
no-useless-concat	Disallow useless concatenation of literals.
no-useless-continue	Disallow useless continue statements.
no-useless-delete-check	Disallow unnecessary existence checks before deletion.
no-useless-else	Disallow else after a statement that exits.
no-useless-error-capture-stack-trace	Disallow unnecessary Error.captureStackTrace(…).
no-useless-fallback-in-spread	Disallow useless fallback when spreading in object literals.
no-useless-iterator-to-array	Disallow unnecessary .toArray() on iterators.
no-useless-length-check	Disallow useless array length check.
no-useless-logical-operand	Disallow unnecessary operands in logical expressions involving boolean literals.
no-useless-override	Disallow useless overrides of class methods.
no-useless-promise-resolve-reject	Disallow returning/yielding Promise.resolve/reject() in async functions or promise callbacks
no-useless-recursion	Disallow simple recursive function calls that can be replaced with a loop.
no-useless-spread	Disallow unnecessary spread.
no-useless-switch-case	Disallow useless case in switch statements.
no-useless-template-literals	Disallow useless template literal expressions.
no-useless-undefined	Disallow useless undefined.
no-xor-as-exponentiation	Disallow the bitwise XOR operator where exponentiation was likely intended.
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.
operator-assignment	Require assignment operator shorthand where possible.
prefer-abort-signal-any	Prefer AbortSignal.any() over manually forwarding abort events between signals.
prefer-abort-signal-timeout	Prefer AbortSignal.timeout() over manually aborting an AbortController with setTimeout().
prefer-add-event-listener	Prefer .addEventListener() and .removeEventListener() over on-functions.
prefer-add-event-listener-options	Prefer an options object over a boolean in .addEventListener().
prefer-aggregate-error	Prefer AggregateError when throwing collected errors.
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() and .filter(…).flatMap(…).
prefer-array-from-async	Prefer Array.fromAsync() over for await…of array accumulation.
prefer-array-from-map	Prefer using the Array.from() mapping function argument.
prefer-array-from-range	Prefer Array.from({length}, …) when creating range arrays.
prefer-array-index-of	Prefer Array#{indexOf,lastIndexOf}() over Array#{findIndex,findLastIndex}() when looking for the index of an item.
prefer-array-iterable-methods	Prefer iterating an array directly or with Array#keys() over Array#entries() when the index or value is unused.
prefer-array-last-methods	Prefer last-oriented array methods over Array#reverse() or Array#toReversed() followed by a method.
prefer-array-slice	Prefer Array#slice() over Array#splice() when reading from the returned array.
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-await	Prefer await over promise chaining.
prefer-bigint-literals	Prefer BigInt literals over the constructor.
prefer-blob-reading-methods	Prefer Blob#arrayBuffer() over FileReader#readAsArrayBuffer(…) and Blob#text() over FileReader#readAsText(…).
prefer-block-statement-over-iife	Prefer block statements over IIFEs used only for scoping.
prefer-boolean-return	Prefer directly returning boolean expressions over if statements.
prefer-class-fields	Prefer class field declarations over this assignments in constructors.
prefer-classlist-toggle	Prefer using Element#classList.toggle() to toggle class names.
prefer-code-point	Prefer String#codePointAt(…) over String#charCodeAt(…) and String.fromCodePoint(…) over String.fromCharCode(…).
prefer-continue	Prefer early continues over whole-loop conditional wrapping.
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-direct-iteration	Prefer direct iteration over default iterator method calls.
prefer-dispose	Prefer using using/await using over manual try/finally resource disposal.
prefer-dom-node-append	Prefer Element#append() over Node#appendChild().
prefer-dom-node-html-methods	Prefer .getHTML() and .setHTML() over .innerHTML.
prefer-dom-node-remove	Prefer childNode.remove() over parentNode.removeChild(childNode).
prefer-dom-node-replace-children	Prefer .replaceChildren() when emptying DOM children.
prefer-dom-node-text-content	Prefer .textContent over .innerText.
prefer-early-return	Prefer early returns over full-function conditional wrapping.
prefer-else-if	Prefer else if over adjacent if statements with related conditions.
prefer-error-is-error	Prefer Error.isError() when checking for errors.
prefer-event-target	Prefer EventTarget over EventEmitter.
prefer-export-from	Prefer export…from when re-exporting.
prefer-flat-math-min-max	Prefer flat Math.min() and Math.max() calls over nested calls.
prefer-get-or-insert-computed	Prefer .getOrInsertComputed() when the default value has side effects.
prefer-global-number-constants	Prefer global numeric constants over Number static properties.
prefer-global-this	Prefer globalThis over window, self, and global.
prefer-group-by	Prefer Object.groupBy() or Map.groupBy() over reduce-based grouping.
prefer-has-check	Prefer .has() when checking existence.
prefer-hoisting-branch-code	Prefer moving code shared by all branches of an if statement out of the branches.
prefer-https	Prefer HTTPS over HTTP.
prefer-identifier-import-export-specifiers	Prefer identifiers over string literals in import and export specifiers.
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-includes-over-repeated-comparisons	Prefer .includes() over repeated equality comparisons.
prefer-iterable-in-constructor	Prefer passing iterables directly to constructors instead of filling empty collections.
prefer-iterator-concat	Prefer Iterator.concat(…) over temporary spread arrays.
prefer-iterator-helpers	Prefer iterator helpers over temporary arrays from iterators.
prefer-iterator-to-array	Prefer Iterator#toArray() over temporary arrays from iterator spreads.
prefer-iterator-to-array-at-end	Prefer moving .toArray() to the end of iterator helper chains.
prefer-keyboard-event-key	Prefer KeyboardEvent#key over deprecated keyboard event properties.
prefer-location-assign	Prefer location.assign() over assigning to location.href.
prefer-logical-operator-over-ternary	Prefer using a logical operator over a ternary.
prefer-map-from-entries	Prefer new Map() over Object.fromEntries() when using the result as a map.
prefer-math-abs	Prefer Math.abs() over manual absolute value expressions and symmetric range checks.
prefer-math-constants	Prefer Math constants over their approximate numeric values.
prefer-math-min-max	Prefer Math.min() and Math.max() over ternaries for simple comparisons.
prefer-math-trunc	Prefer Math.trunc() for truncating numbers.
prefer-minimal-ternary	Prefer moving ternaries into the minimal varying part of an expression.
prefer-modern-dom-apis	Prefer modern DOM APIs.
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-coercion	Prefer Number() over parseFloat() and base-10 parseInt().
prefer-number-is-safe-integer	Prefer Number.isSafeInteger() over integer checks.
prefer-number-properties	Prefer Number static methods over global functions and optionally static properties over global constants.
prefer-object-define-properties	Prefer Object.defineProperties() over multiple Object.defineProperty() calls.
prefer-object-destructuring-defaults	Prefer object destructuring defaults over default object literals with spread.
prefer-object-from-entries	Prefer using Object.fromEntries(…) to transform a list of key-value pairs into an object.
prefer-object-iterable-methods	Prefer the most specific Object iterable method.
prefer-observer-apis	Prefer observer APIs over resize and scroll listeners with layout reads.
prefer-optional-catch-binding	Prefer omitting the catch binding parameter.
prefer-path2d	Prefer Path2D for repeatedly drawn canvas paths.
prefer-private-class-fields	Prefer private class fields over the underscore-prefix convention.
prefer-promise-try	Prefer Promise.try() over promise-wrapping boilerplate.
prefer-promise-with-resolvers	Prefer Promise.withResolvers() when extracting resolver functions from new Promise().
prefer-prototype-methods	Prefer borrowing methods from the prototype instead of the instance.
prefer-query-selector	Prefer .querySelector() and .querySelectorAll() over older DOM query methods.
prefer-queue-microtask	Prefer queueMicrotask() over process.nextTick(), setImmediate(), and setTimeout(…, 0).
prefer-reflect-apply	Prefer Reflect.apply() over Function#apply().
prefer-regexp-escape	Prefer RegExp.escape() for escaping strings to use in regular expressions.
prefer-regexp-test	Prefer RegExp#test() over String#match(), String#search(), and RegExp#exec().
prefer-response-static-json	Prefer Response.json() over new Response(JSON.stringify()).
prefer-scoped-selector	Prefer :scope when using element query selector methods.
prefer-set-has	Prefer Set#has() over Array#includes() when checking for existence or non-existence.
prefer-set-methods	Prefer Set methods for Set operations.
prefer-set-size	Prefer using Set#size instead of Array#length.
prefer-short-arrow-method	Prefer arrow function properties over methods with a single return.
prefer-simple-condition-first	Prefer simple conditions first in logical expressions.
prefer-simple-sort-comparator	Prefer a simple comparison function for Array#sort().
prefer-simplified-conditions	Prefer simplified conditions.
prefer-single-array-predicate	Prefer a single Array#some() or Array#every() with a combined predicate.
prefer-single-call	Enforce combining multiple Array#{push,unshift}(), Element#classList.{add,remove}(), and importScripts() into one call.
prefer-single-object-destructuring	Prefer a single object destructuring declaration per local const source.
prefer-single-replace	Enforce combining multiple single-character replacements into a single String#replaceAll() with a regular expression.
prefer-smaller-scope	Prefer declaring variables in the smallest possible scope.
prefer-split-limit	Prefer String#split() with a limit.
prefer-spread	Prefer the spread operator over Array.from(…), Array#concat(…), Array#{slice,toSpliced}(), and trivial for…of copies.
prefer-string-match-all	Prefer String#matchAll() over RegExp#exec() loops.
prefer-string-pad-start-end	Prefer String#padStart() and String#padEnd() over manual string padding.
prefer-string-raw	Prefer using the String.raw tag to avoid escaping \.
prefer-string-repeat	Prefer String#repeat() for repeated whitespace.
prefer-string-replace-all	Prefer String#replaceAll() over regex searches with the global flag and String#split().join().
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() and String#indexOf() === 0.
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-temporal	Prefer Temporal over Date.
prefer-ternary	Prefer ternary expressions over simple if statements that return or assign values.
prefer-toggle-attribute	Prefer using Element#toggleAttribute() to toggle attributes.
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.
prefer-type-literal-last	Require type literals to be last in union types.
prefer-uint8array-base64	Prefer Uint8Array#toBase64() and Uint8Array.fromBase64() over atob(), btoa(), and Buffer base64 conversions.
prefer-unary-minus	Prefer the unary minus operator over multiplying or dividing by -1.
prefer-unicode-code-point-escapes	Prefer Unicode code point escapes over legacy escape sequences.
prefer-url-can-parse	Prefer URL.canParse() over constructing a URL in a try/catch for validation.
prefer-url-href	Prefer URL#href over stringifying a URL.
prefer-url-search-parameters	Prefer URLSearchParams over manually splitting query strings.
prefer-while-loop-condition	Prefer putting the condition in the while statement.
relative-url-style	Enforce consistent relative URL style.
require-array-join-separator	Enforce using the separator argument with Array#join().
require-array-sort-compare	Require a compare function when calling Array#sort() or Array#toSorted().
require-css-escape	Require CSS.escape() for interpolated values in CSS selectors.
require-module-attributes	Require non-empty module attributes for imports and exports
require-module-specifiers	Require non-empty specifier list in import and export statements.
require-number-to-fixed-digits-argument	Enforce using the digits argument with Number#toFixed().
require-passive-events	Require passive event listeners for high-frequency events.
require-post-message-target-origin	Enforce using the targetOrigin argument with window.postMessage().
require-proxy-trap-boolean-return	Require boolean-returning Proxy traps to return booleans.
string-content	Enforce better string content.
switch-case-braces	Enforce consistent brace style for case clauses.
switch-case-break-position	Enforce consistent break/return/continue/throw position in 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.
try-complexity	Limit the complexity of try blocks.

Non-JavaScript files

While most rules target JavaScript and TypeScript, some also lint other file types when used with the corresponding ESLint language plugin such as @eslint/css, @eslint/json, @eslint/markdown, or @html-eslint/eslint-plugin. Each such rule declares this with the meta.languages field.

When linting JSON, CSS, Markdown, HTML, or other non-JavaScript languages in the same ESLint config, scope Unicorn's JavaScript rule config objects with files. Include TypeScript/JSX extensions there only if your config already provides the matching parser/language setup for those files.

For example, keep Unicorn's JavaScript rules scoped separately, and enable only compatible Unicorn rules in each non-JavaScript language config:

import css from '@eslint/css';
import json from '@eslint/json';
import markdown from '@eslint/markdown';
import html from '@html-eslint/eslint-plugin';
import unicorn from 'eslint-plugin-unicorn';
import {defineConfig} from 'eslint/config';

export default defineConfig([
	{
		files: ['**/*.js'],
		extends: [unicorn.configs.recommended],
	},
	{
		files: ['**/*.json'],
		plugins: {
			json,
			unicorn,
		},
		language: 'json/json',
		rules: {
			'unicorn/no-empty-file': 'error',
			'unicorn/prefer-https': 'error',
		},
	},
	{
		files: ['**/*.css'],
		plugins: {
			css,
			unicorn,
		},
		language: 'css/css',
		rules: {
			'unicorn/prefer-https': 'error',
			'unicorn/text-encoding-identifier-case': 'error',
		},
	},
	{
		files: ['**/*.html'],
		plugins: {
			html,
			unicorn,
		},
		language: 'html/html',
		rules: {
			'unicorn/no-invalid-file-input-accept': 'error',
			'unicorn/prefer-https': 'error',
		},
	},
	{
		files: ['**/*.md'],
		plugins: {
			markdown,
			unicorn,
		},
		language: 'markdown/commonmark',
		rules: {
			'unicorn/expiring-todo-comments': 'error',
			'unicorn/prefer-https': 'error',
		},
	},
]);

These rules work on any file type:

• comment-content
• filename-case
• no-abusive-eslint-disable
• prefer-https

These rules also work on specific non-JavaScript languages:

Name	CSS	HTML	JSON	Markdown
expiring-todo-comments
no-empty-file
no-invalid-file-input-accept
no-manually-wrapped-comments
text-encoding-identifier-case

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 unicorn from 'eslint-plugin-unicorn';
import {defineConfig} from 'eslint/config';

export default defineConfig([
	// …
	{
		files: ['**/*.js'],
		extends: [unicorn.configs.recommended],
		rules: {
			'unicorn/prefer-module': 'warn',
		},
	},
]);

All config

This plugin exports an all config that enables every rule, except deprecated ones.

import unicorn from 'eslint-plugin-unicorn';
import {defineConfig} from 'eslint/config';

export default defineConfig([
	// …
	{
		files: ['**/*.js'],
		extends: [unicorn.configs.all],
		rules: {
			'unicorn/prefer-module': 'warn',
		},
	},
]);

Maintainers

• Sindre Sorhus
• Fisker Cheung