@e18e/eslint-plugin

The official e18e ESLint plugin for modernizing JavaScript/TypeScript code and improving performance.

This plugin focuses on applying the e18e community's best practices and advise to JavaScript/TypeScript codebases.

Overview

There are a few categories of rules in this plugin:

• Modernization - New syntax and APIs which improve code readability and performance
• Module replacements - Community recommended alternatives to popular libraries, focused on performance and size
• Performance improvements - Patterns that can be optimized for better runtime performance

Each of these can be enabled individually, or you can use the recommended configuration to enable all rules.

Installation

npm install --save-dev @e18e/eslint-plugin

Usage

Add the plugin to your eslint.config.js:

import e18e from '@e18e/eslint-plugin';

export default [
  // Use the recommended configuration (includes all categories)
  e18e.configs.recommended,

  // Or use specific category configurations
  e18e.configs.modernization,
  e18e.configs.moduleReplacements,
  e18e.configs.performanceImprovements,

  // Or configure rules manually
  {
    plugins: {
      e18e
    },
    rules: {
      'e18e/prefer-array-at': 'error',
      'e18e/prefer-array-fill': 'error',
      'e18e/prefer-includes': 'error'
    }
  }
];

Usage with oxlint

If you're using oxlint, you can enable the e18e plugin by adding it to your .oxlintrc.json file:

{
  "jsPlugins": ["@e18e/eslint-plugin"],
  "rules": {
    "e18e/prefer-includes": "error"
  }
}

You can enable the recommended configuration by copying the rules from each of the ESLint configuration files into your .oxlintrc.json file.

• modernization configuration
• module replacements configuration
• performance improvements configuration

Copying these rules into your rules object will achieve the same effect as using the recommended configuration in ESLint.

[!NOTE] Our type-aware rules depend on TypeScript ESLint's parser, which means they will not work with oxlint at this time.

Rules

Legend:

• ✅ = Yes / Enabled
• ✖️ = No / Disabled
• 💡 = Has suggestions (requires user confirmation for fixes)
• 🔶 = Optionally uses types (works without TypeScript but more powerful with it)

Modernization

| Rule | Description | Recommended | Fixable | Requires Types | |------|-------------|-------------|---------|----------------| | prefer-array-at | Prefer Array.prototype.at() over length-based indexing | ✅ | ✅ | ✖️ | | prefer-array-fill | Prefer Array.prototype.fill() over Array.from() or map() with constant values | ✅ | ✅ | ✖️ | | prefer-includes | Prefer .includes() over indexOf() comparisons for arrays and strings | ✅ | ✅ | ✖️ | | prefer-array-to-reversed | Prefer Array.prototype.toReversed() over copying and reversing arrays | ✅ | ✅ | ✖️ | | prefer-array-to-sorted | Prefer Array.prototype.toSorted() over copying and sorting arrays | ✅ | ✅ | ✖️ | | prefer-array-to-spliced | Prefer Array.prototype.toSpliced() over copying and splicing arrays | ✅ | ✅ | ✖️ | | prefer-exponentiation-operator | Prefer the exponentiation operator ** over Math.pow() | ✅ | ✅ | ✖️ | | prefer-nullish-coalescing | Prefer nullish coalescing operator (?? and ??=) over verbose null checks | ✅ | ✅ | ✖️ | | prefer-object-has-own | Prefer Object.hasOwn() over Object.prototype.hasOwnProperty.call() and obj.hasOwnProperty() | ✅ | ✅ | ✖️ | | prefer-spread-syntax | Prefer spread syntax over Array.concat(), Array.from(), Object.assign({}, ...), and Function.apply() | ✅ | ✅ | ✖️ | | prefer-url-canparse | Prefer URL.canParse() over try-catch blocks for URL validation | ✅ | 💡 | ✖️ |

Module replacements

| Rule | Description | Recommended | Fixable | Requires Types | |------|-------------|-------------|---------|----------------| | ban-dependencies | Ban dependencies in favor of lighter alternatives | ✅ | ✖️ | ✖️ |

Performance improvements

| Rule | Description | Recommended | Fixable | Requires Types | |------|-------------|-------------|---------|----------------| | no-indexof-equality | Prefer startsWith() for strings and direct array access over indexOf() equality checks | ✖️ | ✅ | ✅ | | prefer-array-from-map | Prefer Array.from(iterable, mapper) over [...iterable].map(mapper) to avoid intermediate array allocation | ✅ | ✅ | ✖️ | | prefer-timer-args | Prefer passing function and arguments directly to setTimeout/setInterval instead of wrapping in an arrow function or using bind | ✅ | ✅ | ✖️ | | prefer-date-now | Prefer Date.now() over new Date().getTime() and +new Date() | ✅ | ✅ | ✖️ | | prefer-regex-test | Prefer RegExp.test() over String.match() and RegExp.exec() when only checking for match existence | ✅ | ✅ | 🔶 |

License

MIT