eslint-config

A reusable eslint config that I use for most of my projects.

Starting at 5.0.0, I only support eslint@^9 or greater.

Installation

npm install -D eslint @mlaursen/eslint-config

Then create an eslint.config.mjs with one of the following:

// @ts-check
import { defineConfig, configs, gitignore } from "@mlaursen/eslint-config";

// somewhat strict type checking
export default defineConfig(
  gitignore(import.meta.url),
  ...configs.frontend("jest")
);

// or with vitest
// export default defineConfig(
//   gitignore(import.meta.url),
//   ...configs.frontend("vitest")
// );

// @ts-check
import { defineConfig, configs, gitignore } from "@mlaursen/eslint-config";

// strict type checking
export default defineConfig(
  gitignore(import.meta.url),
  ...configs.frontendTypeChecking(import.meta.dirname, "jest")
);

// or with vitest
// export default defineConfig(
//   gitignore(import.meta.url),
//   ...configs.frontendTypeChecking(import.meta.dirname, "vitest")
// );

// @ts-check
import { defineConfig, configs, gitignore } from "@mlaursen/eslint-config";

// NOTE: This is recommended for strict type checking. Callable as:
// `cross-env STRICT_TYPING=true eslint "**/*.{ts,tsx,mts,mtsx,js,jsx,mjs,cjs}`
//
// strict type checking with an environment variable. uncomment the following
// line to enable it in your editor
// const strict = true || process.env.STRICT_TYPING === 'true';
const strict = process.env.STRICT_TYPING === "true";
const frontend = strict
  ? configs.frontendTypeChecking(import.meta.dirname, "jest")
  : configs.frontend("jest");

// or with vitest
// const frontend = strict
//   ? configs.frontendTypeChecking(import.meta.dirname, "vitest")
//   : configs.frontend("vitest");
export default defineConfig(gitignore(import.meta.url), ...frontend);

The defineConfig export is the @eslintjs/config.defineConfig() function to provide type definitions and gitignore automatically ignores files from linting based on your .gitignore rules.

Next.js Setup

This is no longer included in this eslint-config since it requires the eslint plugin to be installed in the project to work. Here are the setup steps:

npm install -D @eslint/eslintrc @next/eslint-plugin-next
yarn add -D @eslint/eslintrc @next/eslint-plugin-next
pnpm add -D @eslint/eslintrc @next/eslint-plugin-next

 // @ts-check
+import { FlatCompat } from "@eslint/eslintrc";
 import { defineConfig, configs, gitignore } from "@mlaursen/eslint-config";

+const compat = new FlatCompat({
+  baseDirectory: import.meta.dirname,
+});
+

 // somewhat strict type checking
 export default defineConfig(
   gitignore(import.meta.url),
+  ...compat.config({
+    extends: ["plugin:@next/next/recommended"],
+    // or with core-web-vitals
+    // extends: ["plugin:@next/next/core-web-vitals"],
+  }),
   ...configs.frontend("jest")
 );

Configs

I normally just use the frontend or frontendTypeChecking configs, but the others can be used individually if needed.

• base
• typescript
• typescriptTypeChecking
• testing
• jest
• jestDom
• vitest
• testingLibraryReact
• testingLibraryDom
• react
• jsxA11y
• frontend
• frontendTypeChecking

base

The base config is automatically used by the typescript config and is just the eslint.configs.recommended and a few other stylistic changes.

This should not be used if the typescript or typescriptTypeChecking configs are used.

// @ts-check
import { defineConfig, configs } from "@mlaursen/eslint-config";

export default defineConfig(...configs.base);

typescript

This extends the base config and the tseslint.configs.strict config. It also includes a few stylistic choices for type behavior and disabled strict rules in test files.

Only this rule or typescripttypechecking should be used. They should not be used together.

// @ts-check
import { defineConfig, configs } from "@mlaursen/eslint-config";

export default defineConfig(...configs.typescript);

typescriptTypeChecking

This is the same as the typescript config but also includes the tseslint.configs.strictTypeCheckedOnly config.

Only this rule or typescript should be used. They should not be used together.

// @ts-check
import { defineConfig, configs } from "@mlaursen/eslint-config";

export default defineConfig(
  ...configs.typescriptTypeChecking(import.meta.dirname)
);

testing

This enables the jest or vitest rules along with jestDom.

// @ts-check
import { defineConfig, configs } from "@mlaursen/eslint-config";

export default defineConfig(...configs.testing("jest"));

// or vitest
export default defineConfig(...configs.testing("vitest"));

jest

This only enables the eslint-plugin-jest.configs['flat/recommended] rules on tests files and should not be used if using testing.

// @ts-check
import { defineConfig, configs } from "@mlaursen/eslint-config";

export default defineConfig(...configs.jest);

jestDom

This only enables the eslint-plugin-jest-dom.configs['flat/recommended] rules on tests files and should not be used if using testing.

// @ts-check
import { defineConfig, configs } from "@mlaursen/eslint-config";

export default defineConfig(...configs.jestDom);

vitest

This only enables the @vitest/eslint-plugin rules on test files and should not be used if using testing.

testingLibraryReact

This enables the eslint-plugin-testing-library/.configs["flat/react] plugin and rules on test files.

// @ts-check
import { defineConfig, configs } from "@mlaursen/eslint-config";

export default defineConfig(...configs.vitest);

// @ts-check
import { defineConfig, configs } from "@mlaursen/eslint-config";

export default defineConfig(...configs.testingLibraryReact);

testingLibraryDom

This enables the eslint-plugin-testing-library/.configs["flat/dom] plugin and rules on test files.

This should not be used with the testingLibraryReact rules

// @ts-check
import { defineConfig, configs } from "@mlaursen/eslint-config";

export default defineConfig(...configs.testingLibraryDom);

react

This enables the eslint-plugin-react and eslint-plugin-react-hooks:

// @ts-check
import { defineConfig, configs } from "@mlaursen/eslint-config";

export default defineConfig(...configs.react);

jsxA11y

This enables eslint-plugin-jsx-a11y:

// @ts-check
import { defineConfig, configs } from "@mlaursen/eslint-config";

export default defineConfig(...configs.jsxA11y);

frontend

This is my normal frontend repo setup with react, jsxA11y, jest or vitest, jest-dom, typescript, testing-library/react.

// @ts-check
import { defineConfig, configs } from "@mlaursen/eslint-config";

export default defineConfig(...configs.frontend("jest"));

// or with vitest
export default defineConfig(...configs.frontend("vitest"));

frontendTypeChecking

Same as the frontend, but enables the strict type checking.

// @ts-check
import { defineConfig, configs } from "@mlaursen/eslint-config";

export default defineConfig(...configs.frontendTypeChecking(import.meta.dirname, "jest"));

// or with vitest
export default defineConfig(...configs.frontendTypeChecking(import.meta.dirname, "vitest"));