eslint-plugin-unicorn
More than 100 powerful ESLint rules
You might want to check out XO, which includes this plugin.
Propose or contribute a new rule ➡
Install
npm install --save-dev eslint eslint-plugin-unicorn
eslint.config.js
)
Usage (Requires ESLint >=8.23.0
.
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.
ES Module (Recommended)
import eslintPluginUnicorn from 'eslint-plugin-unicorn';
import * as eslintrc from '@eslint/eslintrc';
export default [
{
languageOptions: {
globals: eslintrc.Legacy.environments.get('es2024'),
},
plugins: {
unicorn: eslintPluginUnicorn,
},
rules: {
'unicorn/better-regex': 'error',
'unicorn/…': 'error',
},
},
// …
];
CommonJS
'use strict';
const eslintPluginUnicorn = require('eslint-plugin-unicorn');
const eslintrc = require('@eslint/eslintrc');
module.exports = [
{
languageOptions: {
globals: eslintrc.Legacy.environments.get('es2024'),
},
plugins: {
unicorn: eslintPluginUnicorn,
},
rules: {
'unicorn/better-regex': 'error',
'unicorn/…': 'error',
},
},
// …
];
.eslintrc.*
or package.json
)
Usage (legacy: Use a preset config or configure each rule in package.json
.
If you don't use the preset, ensure you use the same env
and parserOptions
config as below.
{
"name": "my-awesome-project",
"eslintConfig": {
"env": {
"es2024": true
},
"parserOptions": {
"ecmaVersion": "latest",
"sourceType": "module"
},
"plugins": [
"unicorn"
],
"rules": {
"unicorn/better-regex": "error",
"unicorn/…": "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-destructuring | Use destructured variables over properties. | 🔧 | 💡 | |
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 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-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-push-push | Enforce combining multiple Array#push() into one call. |
✅ | 🔧 | 💡 |
no-array-reduce | Disallow Array#reduce() and Array#reduceRight() . |
✅ | ||
no-await-expression-member | Disallow member access from await expression. | ✅ | 🔧 | |
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-array | Require Array.isArray() instead of instanceof Array . |
✅ | 🔧 | |
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-negated-condition | Disallow negated conditions. | ✅ | 🔧 | |
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-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-await | Disallow awaiting non-promise values. | ✅ | 🔧 | |
no-unnecessary-polyfills | Enforce the use of built-in methods instead of unnecessary polyfills. | ✅ | ||
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}(…) . |
✅ | 🔧 | 💡 |
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-includes | Prefer .includes() over .indexOf() 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-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() . |
✅ | 🔧 | |
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-spread | Prefer the spread operator over Array.from(…) , Array#concat(…) , Array#{slice,toSpliced}() and String#split('') . |
✅ | 🔧 | 💡 |
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-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 throwing an error. |
✅ | 🔧 |
Deprecated Rules
eslint.config.js
)
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.
ES Module (Recommended)
import eslintPluginUnicorn from 'eslint-plugin-unicorn';
export default [
// …
eslintPluginUnicorn.configs['flat/recommended'],
{
rules: {
'unicorn/better-regex': 'warn',
},
},
];
CommonJS
'use strict';
const eslintPluginUnicorn = require('eslint-plugin-unicorn');
module.exports = [
// …
eslintPluginUnicorn.configs['flat/recommended'],
{
rules: {
'unicorn/better-regex': 'warn',
},
},
];
All config
This plugin exports an all
config that makes use of all rules (except for deprecated ones).
ES Module (Recommended)
import eslintPluginUnicorn from 'eslint-plugin-unicorn';
export default [
// …
eslintPluginUnicorn.configs['flat/all'],
{
rules: {
'unicorn/better-regex': 'warn',
},
},
];
CommonJS
'use strict';
const eslintPluginUnicorn = require('eslint-plugin-unicorn');
module.exports = [
// …
eslintPluginUnicorn.configs['flat/all'],
{
rules: {
'unicorn/better-regex': 'warn',
},
},
];
.eslintrc.*
or package.json
)
Preset configs (See the ESLint docs for more information about extending config files.
Note: Preset configs will also enable the correct parser options and environment.
Recommended config
This plugin exports a recommended
config that enforces good practices.
{
"name": "my-awesome-project",
"eslintConfig": {
"extends": "plugin:unicorn/recommended",
"rules": {
"unicorn/better-regex": "warn"
}
}
}
All config
This plugin exports an all
config that makes use of all rules (except for deprecated ones).
{
"name": "my-awesome-project",
"eslintConfig": {
"extends": "plugin:unicorn/all"
}
}