eslint-plugin-unicorn

What is eslint-plugin-unicorn?

The eslint-plugin-unicorn package is a set of ESLint rules that aim to improve code quality by enforcing best practices, preventing common mistakes, and suggesting modern syntax and methods. It includes a variety of rules that are not covered by the core ESLint rules or other plugins, focusing on code enhancements and consistency.

What are eslint-plugin-unicorn's main functionalities?

Filename Case

Enforces a specific case for filenames, which can be configured to be kebab-case, camelCase, or snake_case. This helps maintain consistency in the naming of files across a project.

"unicorn/filename-case": ["error", {"case": "kebabCase"}]

Number Literal Case

Enforces lowercase identifier and uppercase value for number literals, improving readability and consistency in the code.

"unicorn/number-literal-case": "error"

Prevent Abbreviations

Discourages the use of abbreviations in variable names, function names, and other identifiers to improve code clarity and readability.

"unicorn/prevent-abbreviations": ["error", {"replacements": {"temp": false, "err": {"error": true}}}]

Better Regex

Suggests simpler and more optimized regular expressions to improve performance and readability.

"unicorn/better-regex": "error"

Consistent Function Scoping

Enforces that functions are defined at the highest possible level, which can help with readability and reduce the complexity of nested functions.

"unicorn/consistent-function-scoping": "error"

Other packages similar to eslint-plugin-unicorn

eslint-plugin-import

This plugin provides linting rules related to ES2015+ import/export syntax, helping to ensure proper import order, naming, and file path correctness. It is similar to eslint-plugin-unicorn in that it enforces best practices, but it focuses specifically on module import and export issues.

eslint-plugin-promise

This plugin enforces best practices for JavaScript promises. It is similar to eslint-plugin-unicorn in its goal to improve code quality, but it focuses specifically on the use of promises and asynchronous code.

eslint-plugin-jsx-a11y

This plugin checks JSX code for accessibility issues, ensuring that web applications are accessible to users with disabilities. While eslint-plugin-unicorn focuses on general JavaScript code quality, eslint-plugin-jsx-a11y focuses on accessibility concerns in React and JSX.

eslint-plugin-react

This plugin provides React-specific linting rules. It is similar to eslint-plugin-unicorn in that it helps maintain code quality and consistency, but it is tailored specifically for React development.

README

eslint-plugin-unicorn

Various awesome 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

Usage

Configure it in package.json.

{
	"name": "my-awesome-project",
	"eslintConfig": {
		"env": {
			"es6": true
		},
		"parserOptions": {
			"ecmaVersion": 2021,
			"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-push-push": "error",
			"unicorn/no-array-reduce": "error",
			"unicorn/no-console-spaces": "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-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": "off",
			"unicorn/prefer-add-event-listener": "error",
			"unicorn/prefer-array-find": "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-negative-index": "error",
			"unicorn/prefer-number-properties": "error",
			"unicorn/prefer-optional-catch-binding": "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-ternary": "off",
			"unicorn/prefer-type-error": "error",
			"unicorn/prevent-abbreviations": "error",
			"unicorn/string-content": "off",
			"unicorn/throw-new-error": "error"
		}
	}
}

Rules

• better-regex - Improve regexes by making them shorter, consistent, and safer. (fixable)
• catch-error-name - Enforce a specific parameter name in catch clauses. (fixable)
• consistent-destructuring - Use destructured variables over properties. (partly fixable)
• consistent-function-scoping - Move function definitions to the highest possible scope.
• custom-error-definition - Enforce correct Error subclassing. (fixable)
• empty-brace-spaces - Enforce no spaces between braces. (fixable)
• error-message - Enforce passing a message value when creating a built-in error.
• escape-case - Require escape sequences to use uppercase values. (fixable)
• expiring-todo-comments - Add expiration conditions to TODO comments.
• explicit-length-check - Enforce explicitly comparing the length property of a value. (partly fixable)
• filename-case - Enforce a case style for filenames.
• import-index - Enforce importing index files with .. (fixable)
• 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. (partly fixable)
• 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(…). (partly fixable)
• no-array-push-push - Enforce combining multiple Array#push() into one call. (partly fixable)
• no-array-reduce - Disallow Array#reduce() and Array#reduceRight().
• no-console-spaces - Do not use leading/trailing space between console.log parameters. (fixable)
• no-for-loop - Do not use a for loop that can be replaced with a for-of loop. (partly fixable)
• no-hex-escape - Enforce the use of Unicode escapes instead of hexadecimal escapes. (fixable)
• no-instanceof-array - Require Array.isArray() instead of instanceof Array. (fixable)
• 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. (fixable)
• no-nested-ternary - Disallow nested ternary expressions. (partly fixable)
• no-new-array - Disallow new Array(). (partly fixable)
• no-new-buffer - Enforce the use of Buffer.from() and Buffer.alloc() instead of the deprecated new Buffer(). (partly fixable)
• 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-this-assignment - Disallow assigning this to a variable.
• no-unreadable-array-destructuring - Disallow unreadable array destructuring. (partly fixable)
• no-unsafe-regex - Disallow unsafe regular expressions.
• no-unused-properties - Disallow unused object properties.
• no-useless-undefined - Disallow useless undefined. (fixable)
• no-zero-fractions - Disallow number literals with zero fractions or dangling dots. (fixable)
• number-literal-case - Enforce proper case for numeric literals. (fixable)
• numeric-separators-style - Enforce the style of numeric separators by correctly grouping digits. (fixable)
• prefer-add-event-listener - Prefer .addEventListener() and .removeEventListener() over on-functions. (partly fixable)
• prefer-array-find - Prefer .find(…) over the first element from .filter(…). (partly fixable)
• prefer-array-flat-map - Prefer .flatMap(…) over .map(…).flat(). (fixable)
• prefer-array-index-of - Prefer Array#indexOf() over Array#findIndex() when looking for the index of an item. (partly fixable)
• prefer-array-some - Prefer .some(…) over .find(…).
• prefer-date-now - Prefer Date.now() to get the number of milliseconds since the Unix Epoch. (fixable)
• prefer-default-parameters - Prefer default parameters over reassignment. (fixable)
• prefer-dom-node-append - Prefer Node#append() over Node#appendChild(). (fixable)
• prefer-dom-node-dataset - Prefer using .dataset on DOM elements over .setAttribute(…). (fixable)
• prefer-dom-node-remove - Prefer childNode.remove() over parentNode.removeChild(childNode). (fixable)
• prefer-dom-node-text-content - Prefer .textContent over .innerText. (fixable)
• prefer-includes - Prefer .includes() over .indexOf() and Array#some() when checking for existence or non-existence. (partly fixable)
• prefer-keyboard-event-key - Prefer KeyboardEvent#key over KeyboardEvent#keyCode. (partly fixable)
• prefer-math-trunc - Enforce the use of Math.trunc instead of bitwise operators. (partly fixable)
• prefer-modern-dom-apis - Prefer .before() over .insertBefore(), .replaceWith() over .replaceChild(), prefer one of .before(), .after(), .append() or .prepend() over insertAdjacentText() and insertAdjacentElement(). (fixable)
• prefer-negative-index - Prefer negative index over .length - index for {String,Array,TypedArray}#slice() and Array#splice(). (fixable)
• prefer-number-properties - Prefer Number static properties over global ones. (fixable)
• prefer-optional-catch-binding - Prefer omitting the catch binding parameter. (fixable)
• prefer-query-selector - Prefer .querySelector() over .getElementById(), .querySelectorAll() over .getElementsByClassName() and .getElementsByTagName(). (partly fixable)
• prefer-reflect-apply - Prefer Reflect.apply() over Function#apply(). (fixable)
• prefer-regexp-test - Prefer RegExp#test() over String#match() and RegExp#exec(). (fixable)
• prefer-set-has - Prefer Set#has() over Array#includes() when checking for existence or non-existence. (fixable)
• prefer-spread - Prefer the spread operator over Array.from() and Array#concat(). (partly fixable)
• prefer-string-replace-all - Prefer String#replaceAll() over regex searches with the global flag. (fixable)
• prefer-string-slice - Prefer String#slice() over String#substr() and String#substring(). (partly fixable)
• prefer-string-starts-ends-with - Prefer String#startsWith() & String#endsWith() over RegExp#test(). (fixable)
• prefer-string-trim-start-end - Prefer String#trimStart() / String#trimEnd() over String#trimLeft() / String#trimRight(). (fixable)
• prefer-ternary - Prefer ternary expressions over simple if-else statements. (fixable)
• prefer-type-error - Enforce throwing TypeError in type checking conditions. (fixable)
• prevent-abbreviations - Prevent abbreviations. (partly fixable)
• string-content - Enforce better string content. (fixable)
• throw-new-error - Require new when throwing an error. (fixable)

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.

Maintainers

• Sindre Sorhus
• Adam Babcock
• futpib
• Fisker Cheung

Former

• Jeroen Engels
• Sam Verschueren