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eslint-plugin-unicorn Coverage Status

Various awesome ESLint rules

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

Propose or contribute a new rule


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


Configure it in package.json.

	"name": "my-awesome-project",
	"eslintConfig": {
		"env": {
			"es6": true
		"parserOptions": {
			"ecmaVersion": 2021,
			"sourceType": "module"
		"plugins": [
		"rules": {
			"unicorn/better-regex": "error",
			"unicorn/catch-error-name": "error",
			"unicorn/consistent-destructuring": "error",
			"unicorn/consistent-function-scoping": "error",
			"unicorn/custom-error-definition": "off",
			"unicorn/empty-brace-spaces": "error",
			"unicorn/error-message": "error",
			"unicorn/escape-case": "error",
			"unicorn/expiring-todo-comments": "error",
			"unicorn/explicit-length-check": "error",
			"unicorn/filename-case": "error",
			"unicorn/import-index": "off",
			"unicorn/import-style": "error",
			"unicorn/new-for-builtins": "error",
			"unicorn/no-abusive-eslint-disable": "error",
			"unicorn/no-array-callback-reference": "error",
			"unicorn/no-array-for-each": "error",
			"unicorn/no-array-push-push": "error",
			"unicorn/no-array-reduce": "error",
			"unicorn/no-console-spaces": "error",
			"unicorn/no-document-cookie": "error",
			"unicorn/no-for-loop": "error",
			"unicorn/no-hex-escape": "error",
			"unicorn/no-instanceof-array": "error",
			"unicorn/no-keyword-prefix": "off",
			"unicorn/no-lonely-if": "error",
			"no-nested-ternary": "off",
			"unicorn/no-nested-ternary": "error",
			"unicorn/no-new-array": "error",
			"unicorn/no-new-buffer": "error",
			"unicorn/no-null": "error",
			"unicorn/no-object-as-default-parameter": "error",
			"unicorn/no-process-exit": "error",
			"unicorn/no-static-only-class": "error",
			"unicorn/no-this-assignment": "error",
			"unicorn/no-unreadable-array-destructuring": "error",
			"unicorn/no-unsafe-regex": "off",
			"unicorn/no-unused-properties": "off",
			"unicorn/no-useless-undefined": "error",
			"unicorn/no-zero-fractions": "error",
			"unicorn/number-literal-case": "error",
			"unicorn/numeric-separators-style": "error",
			"unicorn/prefer-add-event-listener": "error",
			"unicorn/prefer-array-find": "error",
			"unicorn/prefer-array-flat": "error",
			"unicorn/prefer-array-flat-map": "error",
			"unicorn/prefer-array-index-of": "error",
			"unicorn/prefer-array-some": "error",
			"unicorn/prefer-date-now": "error",
			"unicorn/prefer-default-parameters": "error",
			"unicorn/prefer-dom-node-append": "error",
			"unicorn/prefer-dom-node-dataset": "error",
			"unicorn/prefer-dom-node-remove": "error",
			"unicorn/prefer-dom-node-text-content": "error",
			"unicorn/prefer-includes": "error",
			"unicorn/prefer-keyboard-event-key": "error",
			"unicorn/prefer-math-trunc": "error",
			"unicorn/prefer-modern-dom-apis": "error",
			"unicorn/prefer-module": "error",
			"unicorn/prefer-negative-index": "error",
			"unicorn/prefer-node-protocol": "error",
			"unicorn/prefer-number-properties": "error",
			"unicorn/prefer-optional-catch-binding": "error",
			"unicorn/prefer-prototype-methods": "error",
			"unicorn/prefer-query-selector": "error",
			"unicorn/prefer-reflect-apply": "error",
			"unicorn/prefer-regexp-test": "error",
			"unicorn/prefer-set-has": "error",
			"unicorn/prefer-spread": "error",
			"unicorn/prefer-string-replace-all": "off",
			"unicorn/prefer-string-slice": "error",
			"unicorn/prefer-string-starts-ends-with": "error",
			"unicorn/prefer-string-trim-start-end": "error",
			"unicorn/prefer-switch": "error",
			"unicorn/prefer-ternary": "error",
			"unicorn/prefer-type-error": "error",
			"unicorn/prevent-abbreviations": "error",
			"unicorn/string-content": "off",
			"unicorn/throw-new-error": "error"


Each rule has emojis denoting:

  • if it belongs to the recommended configuration
  • 🔧 if some problems reported by the rule are automatically fixable by the --fix command line option
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-index Enforce importing index files with .. 🔧
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-array-callback-reference Prevent passing a function reference directly to iterator methods.
no-array-for-each Prefer for…of over Array#forEach(…). 🔧
no-array-push-push Enforce combining multiple Array#push() into one call. 🔧
no-array-reduce Disallow Array#reduce() and Array#reduceRight().
no-console-spaces Do not use leading/trailing space between console.log parameters. 🔧
no-document-cookie Do not use document.cookie directly.
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-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-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 Forbid classes that only have static members. 🔧
no-this-assignment Disallow assigning this to a variable.
no-unreadable-array-destructuring Disallow unreadable array destructuring. 🔧
no-unsafe-regex Disallow unsafe regular expressions.
no-unused-properties Disallow unused object properties.
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(…) over the first 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() over Array#findIndex() when looking for the index of an item. 🔧
prefer-array-some Prefer .some(…) over .find(…).
prefer-date-now Prefer 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 .setAttribute(…). 🔧
prefer-dom-node-remove Prefer childNode.remove() over parentNode.removeChild(childNode). 🔧
prefer-dom-node-text-content Prefer .textContent over .innerText. 🔧
prefer-includes Prefer .includes() over .indexOf() and Array#some() when checking for existence or non-existence. 🔧
prefer-keyboard-event-key Prefer KeyboardEvent#key over KeyboardEvent#keyCode. 🔧
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-module Prefer JavaScript modules (ESM) over CommonJS. 🔧
prefer-negative-index Prefer negative index over .length - index for {String,Array,TypedArray}#slice(), Array#splice() and Array#at(). 🔧
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-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-spread Prefer the spread operator over Array.from(…), Array#concat(…) and Array#slice(). 🔧
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-type-error Enforce throwing TypeError in type checking conditions. 🔧
prevent-abbreviations Prevent abbreviations. 🔧
string-content Enforce better string content. 🔧
throw-new-error Require new when throwing an error. 🔧

Deprecated Rules

See docs/

Recommended config

This plugin exports a recommended config that enforces good practices.

Enable it in your package.json with the extends option:

	"name": "my-awesome-project",
	"eslintConfig": {
		"extends": "plugin:unicorn/recommended"

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

Note: This config will also enable the correct parser options and environment.