eslint-config-kevlar

Shareable ESLint 10 + Prettier flat config for TypeScript, React 19 and Next.js 16 projects.

Import it, compose it, done. The rules live in this package — there are no files to copy and no setup command to run. Upgrade by bumping the version.

Install

Pick the line for your project type. ESLint, Prettier and TypeScript stay your project's own dependencies (they are peers); everything else comes with the package.

# TypeScript / Node library
npm install --save-dev eslint-config-kevlar eslint prettier typescript

# React or Next.js app (react / react-dom / next are your app's own deps)
npm install --save-dev eslint-config-kevlar eslint prettier typescript

pnpm and yarn work the same way (pnpm add -D ..., yarn add -D ...).

Usage

Create eslint.config.mjs in your project root.

TypeScript / Node

import kevlar from 'eslint-config-kevlar';

export default kevlar;

React

import kevlar from 'eslint-config-kevlar';
import react from 'eslint-config-kevlar/react';

export default [...kevlar, ...react];

Next.js

import kevlar from 'eslint-config-kevlar';
import next from 'eslint-config-kevlar/next';

export default [...kevlar, ...next];

The next entry includes the React rules, so you do not need to add ./react as well.

Prettier

Add one key to your package.json — no .prettierrc file needed:

{
  "prettier": "eslint-config-kevlar/prettier"
}

Entry points

| Import | What it provides | | ------------------------------- | ----------------------------------------------------------------------- | | eslint-config-kevlar | Base: TypeScript (recommended + strict), Vitest test rules, Prettier | | eslint-config-kevlar/react | React rules (@eslint-react) + React 19 Hooks/Compiler rules | | eslint-config-kevlar/next | Everything in /react plus Next.js core-web-vitals + Server Components | | eslint-config-kevlar/prettier | The Prettier options, for the package.json prettier key |

Rules at a glance

• No any (@typescript-eslint/no-explicit-any), no non-null assertions
• Explicit function return types (expressions and typed expressions exempt)
• Unused variables must be prefixed with _
• Single quotes, semicolons required, no trailing commas, newline at end of file
• Prettier-enforced formatting, printWidth 180, 2-space indentation
• Vitest: no focused (it.only) or disabled (it.skip) tests in committed code
• React 19: rules of hooks, exhaustive deps and the React Compiler rule set
• Next.js: Core Web Vitals rules and React Server Components checks

Extending and overriding

Append your own flat-config objects after the spread:

import kevlar from 'eslint-config-kevlar';

export default [
  ...kevlar,
  {
    rules: {
      'no-console': 'error'
    }
  }
];

Compatibility

| Tool | Supported range | | ---------- | --------------------- | | eslint | ^9.0.0 \|\| ^10.0.0 | | prettier | ^3.0.0 | | typescript | >=5.9.0 <6.1.0 |

Migrating from v2

• Stop running npx eslint-config-kevlar — there is no setup/scaffold command anymore.
• Replace your generated eslint.config.mjs with the three-line stub above for your project type.
• Move Prettier to the package.json key shown above. An existing .prettierrc still works if you prefer to keep one; the package key is just the no-file option.
• The React layer now uses @eslint-react (the previous eslint-plugin-react does not install on ESLint 10). Rule names under React change accordingly; the previous react/prop-types and react/react-in-jsx-scope toggles are no longer needed.

License

ISC