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, Markdown, SOML, TOML, and YAML 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 recommended-css configuration.
🌐 Set in the recommended-html configuration.
🧩 Set in the recommended-json configuration.
📚 Set in the recommended-markdown configuration.
💎 Set in the recommended-soml configuration.
🛠️ Set in the recommended-toml configuration.
📋 Set in the recommended-yaml 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.	✅		💡
comma-spacing	Enforce consistent spacing before and after commas in JSON and SOML.		🔧
comment-content	Enforce better comment content.		🔧
consistent-arrow-return-style	Enforce a consistent return style for multiline arrow function bodies.		🔧
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.	✅ ☑️
indent	Enforce consistent indentation in JSON and CSS.		🔧
isolated-functions	Prevent usage of variables from outside the scope of isolated functions.	✅
iteration-fallback-style	Enforce a consistent style for optional loop sources.		🔧
key-name-casing	Enforce a case style for data keys.
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 and shared indentation in multiline comments.	✅ 🎨 🧩 💎	🔧
no-async-iterator-callback	Disallow asynchronous callbacks in synchronous iterator helpers.	✅ ☑️
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-barrel-files	Disallow barrel files.
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 optionally 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-conflicting-constraints	Disallow conflicting CSS query and HTML form constraints.	✅ 🎨 🌐 ☑️
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-empty-link-text	Disallow empty link text in Markdown.	📚
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 assignment and initialization immediately after declaration.	✅	🔧	💡
no-impossible-length-comparison	Disallow impossible comparisons against .length or .size.	✅ ☑️
no-incomplete-accessor-override	Disallow class accessors that hide an inherited getter or setter.	✅ ☑️
no-incorrect-query-selector	Disallow incorrect querySelector() and querySelectorAll() usage.	✅	🔧
no-incorrect-template-string-interpolation	Disallow incorrect template literal interpolation syntax.	✅		💡
no-ineffective-csp-directives	Disallow ineffective CSP directives in <meta> elements.	✅ 🌐 ☑️
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-boolean-attribute-value	Disallow invalid values for HTML boolean attributes.	✅ ☑️		💡
no-invalid-character-comparison	Disallow comparing a single character from a string to a multi-character string.	✅ ☑️
no-invalid-dom-token	Disallow invalid DOM tokens.	✅ ☑️		💡
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-integrity	Disallow invalid subresource integrity metadata.	✅ 🌐 ☑️
no-invalid-intl-options	Disallow invalid or ignored Intl options.	✅ ☑️		💡
no-invalid-property-descriptor	Disallow invalid property descriptors.	✅ ☑️		💡
no-invalid-remove-event-listener	Prevent calling EventTarget#removeEventListener() with the result of an expression.	✅ ☑️
no-invalid-response-options	Disallow invalid options in new Response(), Response.json(), and Response.redirect().	✅ ☑️		💡
no-invalid-style-set-property	Disallow invalid arguments to CSSStyleDeclaration#setProperty().	✅ ☑️		💡
no-invalid-temporal-arithmetic	Disallow statically known invalid Temporal arithmetic.	✅ ☑️		💡
no-invalid-url-protocol-comparison	Disallow invalid protocol strings in comparisons with URL#protocol.	✅ ☑️	🔧
no-invalid-well-known-symbol-methods	Disallow invalid implementations of well-known symbol methods.	✅ ☑️	🔧	💡
no-javascript-url	Disallow javascript: URLs in Markdown.
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-leading-empty-lines	Disallow empty lines at the beginning of a file.	✅ 🎨 🌐 🧩 📚 💎 🛠️ 📋	🔧
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-loss-of-precision	Disallow numeric literals that lose precision when represented as IEEE 754 binary64 values.
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-missing-local-resource	Disallow references to missing local resources.		🔧
no-multiple-promise-resolver-calls	Disallow calling Promise executor resolver functions more than once on the same execution path.	✅ ☑️
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-prevent-default-in-passive-listener	Disallow ineffective preventDefault() calls in passive event listeners.	✅ ☑️		💡
no-process-exit	Disallow process.exit().	✅ ☑️
no-redundant-comparison	Disallow comparisons made redundant by an equality check in the same logical AND.	✅ ☑️	🔧	💡
no-repeated-call-wrappers	Disallow repeating the same wrapper at every call to a function.
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-shorthand-property-overrides	Disallow shorthand properties that override related longhand properties.	✅ 🎨 ☑️
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-transition-all	Disallow all as a transition property.	✅ 🎨 ☑️
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 unnecessary use of Array#flatMap().	✅	🔧	💡
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-default-arguments	Disallow arguments that match their parameter defaults.		🔧	💡
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-parameters	Disallow parameters that receive the same value at every call.	✅	🔧	💡
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-unnecessary-string-trim	Disallow String#trim() before String#startsWith() or String#endsWith().	✅ ☑️	🔧
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-json-serialization	Disallow known values that JSON serialization cannot represent faithfully.	✅		💡
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-sqlite-interpolation	Disallow interpolation into SQL strings passed to Node’s node:sqlite APIs.	✅ ☑️
no-unsafe-string-replacement	Disallow non-literal replacement values in String#replace() and String#replaceAll().	✅
no-unused-builtin-method-return	Disallow ignoring the return value of selected built-in methods.	✅ ☑️
no-unused-iterator-helper	Disallow discarding lazy iterator helpers.	✅ ☑️		💡
no-unused-properties	Disallow unused object properties.
no-url-in-search-params	Disallow passing full URLs to URLSearchParams.	✅ ☑️		💡
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-re-export	Disallow redundant re-exports.	✅ ☑️
no-useless-recursion	Disallow simple recursive function calls that can be replaced with a loop.	✅
no-useless-set-construction	Disallow unnecessary Set construction around Set methods.	✅ ☑️	🔧
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.	✅ ☑️

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