eslint-plugin-unicorn

Various awesome ESLint rules

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

Install

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

Usage

Configure it in package.json.

{
	"name": "my-awesome-project",
	"eslintConfig": {
		"env": {
			"es6": true
		},
		"parserOptions": {
			"ecmaVersion": "latest",
			"sourceType": "module"
		},
		"plugins": [
			"unicorn"
		],
		"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-method-this-argument": "error",
			"unicorn/no-array-push-push": "error",
			"unicorn/no-array-reduce": "error",
			"unicorn/no-await-expression-member": "error",
			"unicorn/no-console-spaces": "error",
			"unicorn/no-document-cookie": "error",
			"unicorn/no-empty-file": "error",
			"unicorn/no-for-loop": "error",
			"unicorn/no-hex-escape": "error",
			"unicorn/no-instanceof-array": "error",
			"unicorn/no-invalid-remove-event-listener": "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-fallback-in-spread": "error",
			"unicorn/no-useless-length-check": "error",
			"unicorn/no-useless-spread": "error",
			"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-at": "off",
			"unicorn/prefer-code-point": "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-export-from": "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-object-from-entries": "error",
			"unicorn/prefer-object-has-own": "off",
			"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-top-level-await": "off",
			"unicorn/prefer-type-error": "error",
			"unicorn/prevent-abbreviations": "error",
			"unicorn/require-array-join-separator": "error",
			"unicorn/require-number-to-fixed-digits-argument": "error",
			"unicorn/require-post-message-target-origin": "off",
			"unicorn/string-content": "off",
			"unicorn/template-indent": "warn",
			"unicorn/throw-new-error": "error"
		}
	}
}

Rules

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
💡 if some problems reported by the rule are 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-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-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	Forbid 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-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-fallback-in-spread	Forbid useless fallback when spreading in object literals.	✅	🔧
no-useless-length-check	Disallow useless array length check.	✅	🔧
no-useless-spread	Disallow unnecessary spread.	✅	🔧
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 `.filter(…).length` check and `.find(…)`.	✅	🔧	💡
prefer-at	Prefer `.at()` method for index access and `String#charAt()`.		🔧	💡
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 `.setAttribute(…)`.	✅	🔧
prefer-dom-node-remove	Prefer `childNode.remove()` over `parentNode.removeChild(childNode)`.	✅	🔧	💡
prefer-dom-node-text-content	Prefer `.textContent` over `.innerText`.	✅		💡
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-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-object-from-entries	Prefer using `Object.fromEntries(…)` to transform a list of key-value pairs into an object.	✅	🔧
prefer-object-has-own	Prefer `Object.hasOwn(…)` over `Object.prototype.hasOwnProperty.call(…)`.		🔧
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(…)`, `Array#slice()` 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.	✅	🔧
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.		🔧	💡
template-indent	Fix whitespace-insensitive template indentation.		🔧
throw-new-error	Require `new` when throwing an error.	✅	🔧

Deprecated Rules

See docs/deprecated-rules.md

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.

All config

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

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

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

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

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