# @e18e/eslint-plugin

> The official e18e ESLint plugin for modernizing code and improving performance.

Latest version **0.8.0** (published 2026-08-05) · MIT license · 0 weekly downloads

## Install

```sh
npm install @e18e/eslint-plugin
pnpm add @e18e/eslint-plugin
yarn add @e18e/eslint-plugin
bun add @e18e/eslint-plugin
```

## Health

**Score 55/100 (C)** — status: active.

Positive: no vulnerabilities; recently updated; high maintenance score.

Warnings: low downloads; no types; no esm support; pre 1.0.

## Facts

| | |
|---|---|
| Version | 0.8.0 |
| Published | 2026-08-05 |
| First published | 2025-12-19 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | none |
| Module format | CommonJS |
| Dependencies | 0 |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 205 |
| Author | James Garbutt |
| Maintainers | 43081j |
| Keywords | eslint, e18e, performance, bloat, perf |

## Links

- npm: https://www.npmjs.com/package/@e18e/eslint-plugin
- Repository: https://github.com/e18e/eslint-plugin
- Homepage: https://github.com/e18e/eslint-plugin#readme
- Issues: https://github.com/e18e/eslint-plugin/issues
- npm.io page: https://npm.io/package/@e18e/eslint-plugin

## Alternatives

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## Recent versions

- 0.8.0 (latest) — 2026-08-05
- 0.6.0 — 2026-07-24
- 0.5.1 — 2026-06-14
- 0.5.0 — 2026-05-12
- 0.4.1 — 2026-04-28
- 0.3.0 — 2026-03-22
- 0.2.0 — 2026-02-16
- 0.1.4 — 2026-01-28
- 0.1.3 — 2025-12-21
- 0.1.2 — 2025-12-19
- 0.1.1 — 2025-12-19
- 0.1.0 — 2025-12-19
- 0.0.1 — 2025-12-19

## README

# @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

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

## Usage

Add the plugin to your `eslint.config.js`:

```ts
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:

```json
{
  "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](./src/configs/modernization.ts)
- [module replacements configuration](./src/configs/module-replacements.ts)
- [performance improvements configuration](./src/configs/performance-improvements.ts)

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.

## Linting `package.json`

Some rules (e.g. `ban-dependencies`) can be used against your `package.json`.

You can achieve this by using `@eslint/json` or `jsonc-eslint-parser`.

For example, with `@eslint/json` and `eslint.config.js`:

```ts
import e18e from '@e18e/eslint-plugin';
import json from '@eslint/json';
import {defineConfig} from 'eslint/config';

export default defineConfig([
  {
    files: ['package.json'],
    language: 'json/json',
    plugins: {
      e18e,
      json
    },
    extends: ['e18e/recommended'],
  }
]);
```

Or with `jsonc-eslint-parser` and `eslint.config.js`:

```ts
import e18e from '@e18e/eslint-plugin';
import jsonParser from 'jsonc-eslint-parser';
import {defineConfig} from 'eslint/config';

export default defineConfig([
  {
    files: ['package.json'],
    languageOptions: {
      parser: jsonParser
    },
    plugins: {
      e18e
    },
    extends: ['e18e/recommended'],
  }
]);
```

Read more at the
[`@eslint/json` docs](https://github.com/eslint/json) and
[`jsonc-eslint-parser` docs](https://github.com/ota-meshi/jsonc-eslint-parser).

## 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](./src/rules/prefer-array-at.ts) | Prefer `Array.prototype.at()` over length-based indexing | ✅ | ✅ | 🔶 |
| [prefer-array-fill](./src/rules/prefer-array-fill.ts) | Prefer `Array.prototype.fill()` over `Array.from()` or `map()` with constant values | ✅ | ✅ | ✖️ |
| [prefer-includes](./src/rules/prefer-includes.ts) | Prefer `.includes()` over `indexOf()` comparisons for arrays and strings | ✅ | ✅ | ✖️ |
| [prefer-array-to-reversed](./src/rules/prefer-array-to-reversed.ts) | Prefer `Array.prototype.toReversed()` over copying and reversing arrays | ✅ | ✅ | 🔶 |
| [prefer-array-to-sorted](./src/rules/prefer-array-to-sorted.ts) | Prefer `Array.prototype.toSorted()` over copying and sorting arrays | ✅ | ✅ | 🔶 |
| [prefer-array-to-spliced](./src/rules/prefer-array-to-spliced.ts) | Prefer `Array.prototype.toSpliced()` over copying and splicing arrays | ✅ | ✅ | ✖️ |
| [prefer-exponentiation-operator](./src/rules/prefer-exponentiation-operator.ts) | Prefer the exponentiation operator `**` over `Math.pow()` | ✅ | ✅ | ✖️ |
| [prefer-nullish-coalescing](./src/rules/prefer-nullish-coalescing.ts) | Prefer nullish coalescing operator (`??` and `??=`) over verbose null checks | ✅ | ✅ | ✖️ |
| [prefer-object-has-own](./src/rules/prefer-object-has-own.ts) | Prefer `Object.hasOwn()` over `Object.prototype.hasOwnProperty.call()` and `obj.hasOwnProperty()` | ✅ | ✅ | ✖️ |
| [prefer-spread-syntax](./src/rules/prefer-spread-syntax.ts) | Prefer spread syntax over `Array.concat()`, `Array.from()`, `Object.assign({}, ...)`, and `Function.apply()` | ✅ | ✅ | 🔶 |
| [prefer-url-canparse](./src/rules/prefer-url-canparse.ts) | Prefer `URL.canParse()` over try-catch blocks for URL validation | ✅ | 💡 | ✖️ |
| [prefer-get-or-insert](./src/rules/prefer-get-or-insert.ts) | Prefer `Map.prototype.getOrInsert()` over reading a map entry with a default and writing it back | ✖️ | ✅ | ✖️ |

### Module replacements

| Rule | Description | Recommended | Fixable | Requires Types |
|------|-------------|-------------|---------|----------------|
| [ban-dependencies](./src/rules/ban-dependencies.ts) | Disallow dependencies in favor of more performant or secure alternatives | ✅ | ✖️ | ✖️ |

### Performance improvements

| Rule | Description | Recommended | Fixable | Requires Types |
|------|-------------|-------------|---------|----------------|
| [no-indexof-equality](./src/rules/no-indexof-equality.ts) | Prefer `startsWith()` for strings and direct array access over `indexOf()` equality checks | ✖️ | ✅ | ✅ |
| [prefer-array-from-map](./src/rules/prefer-array-from-map.ts) | Prefer `Array.from(iterable, mapper)` over `[...iterable].map(mapper)` to avoid intermediate array allocation | ✅ | ✅ | ✖️ |
| [prefer-array-some](./src/rules/prefer-array-some.ts) | Prefer `Array.some()` over `Array.find()` and `Array.filter().length` checks when checking for element existence | ✅ | ✅ | ✖️ |
| [prefer-timer-args](./src/rules/prefer-timer-args.ts) | Prefer passing function and arguments directly to `setTimeout`/`setInterval` instead of wrapping in an arrow function or using `bind` | ✅ | ✅ | ✖️ |
| [prefer-date-now](./src/rules/prefer-date-now.ts) | Prefer `Date.now()` over `new Date().getTime()` and `+new Date()` | ✅ | ✅ | ✖️ |
| [prefer-regex-test](./src/rules/prefer-regex-test.ts) | Prefer `RegExp.test()` over `String.match()` and `RegExp.exec()` when only checking for match existence | ✅ | ✅ | 🔶 |
| [prefer-static-regex](./src/rules/prefer-static-regex.ts) | Prefer defining regular expressions at module scope to avoid re-compilation on every function call | ✅ | ✖️ | 🔶 |
| [prefer-inline-equality](./src/rules/prefer-inline-equality.ts) | Prefer inline equality checks over temporary object creation for simple comparisons | ✖️ | ✅ | 🔶 |
| [prefer-string-fromcharcode](./src/rules/prefer-string-fromcharcode.ts) | Prefer `String.fromCharCode()` over `String.fromCodePoint()` for code points below `0x10000` | ✅ | ✅ | ✖️ |
| [prefer-includes-over-regex-test](./src/rules/prefer-includes-over-regex-test.ts) | Prefer `s.includes()` / `startsWith` / `endsWith` over `/literal/.test(s)` when the regex has no metacharacters or flags | ✖️ | ✅ | ✖️ |
| [prefer-charcode-at-in-loop](./src/rules/prefer-charcode-at-in-loop.ts) | Prefer `charCodeAt()` over indexed string access for single-character comparisons inside loops | ✖️ | 💡 | 🔶 |
| [prefer-throw-if-no-entry](./src/rules/prefer-throw-if-no-entry.ts) | Prefer `{throwIfNoEntry: false}` over relying on a thrown error for missing fs entries from sync stat calls | ✖️ | 💡 | ✖️ |
| [no-delete-property](./src/rules/no-delete-property.ts) | Disallow `delete` on properties — V8 deoptimizes the object to dictionary mode | ✖️ | 💡 | ✖️ |
| [prefer-flatmap-over-map-flat](./src/rules/prefer-flatmap-over-map-flat.ts) | Prefer `Array.prototype.flatMap()` over `.map(fn).flat()` to skip the intermediate array | ✖️ | ✅ | ✖️ |
| [prefer-slice-over-split-index](./src/rules/prefer-slice-over-split-index.ts) | Prefer `indexOf(needle)` and `slice(...)` over `split()[N]` when splitting a string into two pieces | ✖️ | ✖️ | ✖️ |
| [no-spread-in-reduce](./src/rules/no-spread-in-reduce.ts) | Disallow spreading the accumulator inside a `.reduce()` callback — it's O(N²) | ✖️ | ✖️ | ✖️ |
| [prefer-static-collator](./src/rules/prefer-static-collator.ts) | Prefer hoisting an `Intl.Collator` over calling `localeCompare` inside a `sort`/`toSorted` callback | ✖️ | ✖️ | ✖️ |

## Sponsors

<p align="center">
  <a href="https://e18e.dev/sponsor">
    <img src="https://e18e.dev/sponsors.svg" alt="e18e community sponsors" />
  </a>
</p>

## License

MIT

---
_Source: https://npm.io/package/@e18e/eslint-plugin · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._