eslint-config-janfr

• Single quotes, no semi
• Auto fix for formatting (aimed to be used standalone without Prettier)
• Sorted imports, dangling commas
• Reasonable defaults, best practices, only one line of config
• Designed to work with TypeScript, JSX, Vue out-of-box
• Lints also for json, yaml, toml, markdown, html, xml
• Opinionated, but very customizable
• ESLint Flat config, compose easily!
• Using ESLint Stylistic
• Respects .gitignore by default
• Optional React, Svelte, UnoCSS, Astro support
• Optional formatters support for CSS, HTML, etc.
• Style principle: Minimal for reading, stable for diff, consistent

Usage

Wizard

We provided a CLI tool to help you set up your project, or migrate from the legacy config to the new flat config.

npx eslint-config-janfr@latest

Install

pnpm i -D eslint eslint-config-janfr

Create config file

With "type": "module" in package.json (recommended):

// eslint.config.js
import bclint from 'eslint-config-janfr'

export default bclint()

With CJS:

// eslint.config.js
const bclint = require('eslint-config-janfr').default

module.exports = bclint()

[!TIP] ESLint only detects eslint.config.js as the flat config entry, meaning you need to put type: module in your package.json or you have to use CJS in eslint.config.js. If you want explicit extension like .mjs or .cjs, or even eslint.config.ts, you can install eslint-ts-patch to fix it.

Combined with legacy config:

// eslint.config.js
const bclint = require('eslint-config-janfr').default
const { FlatCompat } = require('@eslint/eslintrc')

const compat = new FlatCompat()

module.exports = bclint(
  {
    ignores: [],
  },

  // Legacy config
  ...compat.config({
    extends: [
      'eslint:recommended',
      // Other extends...
    ],
  })

  // Other flat configs...
)

Note that .eslintignore no longer works in Flat config, see customization for more details.

Add script for package.json

For example:

{
  "scripts": {
    "lint": "eslint .",
    "lint:fix": "eslint . --fix"
  }
}

VS Code support (auto fix)

Install VS Code ESLint extension

Add the following settings to your .vscode/settings.json:

{
  // Enable the ESlint flat config support
  "eslint.experimental.useFlatConfig": true,

  // Disable the default formatter, use eslint instead
  "prettier.enable": false,
  "editor.formatOnSave": false,

  // Auto fix
  "editor.codeActionsOnSave": {
    "source.fixAll.eslint": "explicit",
    "source.organizeImports": "never"
  },

  // Silent the stylistic rules in you IDE, but still auto fix them
  "eslint.rules.customizations": [
    { "rule": "style/*", "severity": "off" },
    { "rule": "format/*", "severity": "off" },
    { "rule": "*-indent", "severity": "off" },
    { "rule": "*-spacing", "severity": "off" },
    { "rule": "*-spaces", "severity": "off" },
    { "rule": "*-order", "severity": "off" },
    { "rule": "*-dangle", "severity": "off" },
    { "rule": "*-newline", "severity": "off" },
    { "rule": "*quotes", "severity": "off" },
    { "rule": "*semi", "severity": "off" }
  ],

  // Enable eslint for all supported languages
  "eslint.validate": [
    "javascript",
    "javascriptreact",
    "typescript",
    "typescriptreact",
    "vue",
    "html",
    "markdown",
    "json",
    "jsonc",
    "yaml",
    "toml",
    "xml"
  ]
}

Customization

Since v1.0, we migrated to ESLint Flat config. It provides much better organization and composition.

Normally you only need to import the bclint preset:

// eslint.config.js
import bclint from 'eslint-config-janfr'

export default bclint()

And that's it! Or you can configure each integration individually, for example:

// eslint.config.js
import bclint from 'eslint-config-janfr'

export default bclint({
  // Enable stylistic formatting rules
  // stylistic: true,

  // Or customize the stylistic rules
  stylistic: {
    indent: 2, // 4, or 'tab'
    quotes: 'single', // or 'double'
  },

  // TypeScript and Vue are auto-detected, you can also explicitly enable them:
  typescript: true,
  vue: true,

  // Disable jsonc and yaml support
  jsonc: false,
  yaml: false,

  // `.eslintignore` is no longer supported in Flat config, use `ignores` instead
  ignores: [
    '**/fixtures',
    // ...globs
  ]
})

The bclint factory function also accepts any number of arbitrary custom config overrides:

// eslint.config.js
import bclint from 'eslint-config-janfr'

export default bclint(
  {
    // Configures for bclint's config
  },

  // From the second arguments they are ESLint Flat Configs
  // you can have multiple configs
  {
    files: ['**/*.ts'],
    rules: {},
  },
  {
    rules: {},
  },
)

Going more advanced, you can also import fine-grained configs and compose them as you wish:

We wouldn't recommend using this style in general unless you know exactly what they are doing, as there are shared options between configs and might need extra care to make them consistent.

// eslint.config.js
import {
  combine,
  comments,
  html,
  ignores,
  imports,
  javascript,
  jsdoc,
  jsonc,
  markdown,
  node,
  sortPackageJson,
  sortTsconfig,
  stylistic,
  toml,
  typescript,
  unicorn,
  vue,
  xml,
  yaml,
} from 'eslint-config-janfr'

export default combine(
  ignores(),
  javascript(/* Options */),
  comments(),
  html(),
  node(),
  jsdoc(),
  imports(),
  unicorn(),
  typescript(/* Options */),
  stylistic(),
  vue(),
  jsonc(),
  yaml(),
  toml(),
  markdown(),
  xml(),
)

Check out the configs and factory for more details.

Thanks to sxzz/eslint-config for the inspiration and reference.

Plugins Renaming

Since flat config requires us to explicitly provide the plugin names (instead of the mandatory convention from npm package name), we renamed some plugins to make the overall scope more consistent and easier to write.

| New Prefix | Original Prefix | Source Plugin | | ---------- | ---------------------- | ------------------------------------------------------------------------------------------ | | import/* | i/* | eslint-plugin-i | | node/* | n/* | eslint-plugin-n | | yaml/* | yml/* | eslint-plugin-yml | | html/* | @html-eslint/* | @html-eslint/eslint-plugin | | ts/* | @typescript-eslint/* | @typescript-eslint/eslint-plugin | | style/* | @stylistic/* | @stylistic/eslint-plugin | | test/* | vitest/* | eslint-plugin-vitest | | test/* | no-only-tests/* | eslint-plugin-no-only-tests |

When you want to override rules, or disable them inline, you need to update to the new prefix:

-// eslint-disable-next-line @typescript-eslint/consistent-type-definitions
+// eslint-disable-next-line ts/consistent-type-definitions
type foo = { bar: 2 }

Rules Overrides

Certain rules would only be enabled in specific files, for example, ts/* rules would only be enabled in .ts files and vue/* rules would only be enabled in .vue files. If you want to override the rules, you need to specify the file extension:

// eslint.config.js
import bclint from 'eslint-config-janfr'

export default bclint(
  {
    vue: true,
    typescript: true
  },
  {
    // Remember to specify the file glob here, otherwise it might cause the vue plugin to handle non-vue files
    files: ['**/*.vue'],
    rules: {
      'vue/operator-linebreak': ['error', 'before'],
    },
  },
  {
    // Without `files`, they are general rules for all files
    rules: {
      'style/semi': ['error', 'never'],
    },
  }
)

We also provided a overrides options in each integration to make it easier:

// eslint.config.js
import bclint from 'eslint-config-janfr'

export default bclint({
  vue: {
    overrides: {
      'vue/operator-linebreak': ['error', 'before'],
    },
  },
  typescript: {
    overrides: {
      'ts/consistent-type-definitions': ['error', 'interface'],
    },
  },
  yaml: {
    overrides: {
      // ...
    },
  },
})

Optional Configs

We provide some optional configs for specific use cases, that we don't include their dependencies by default.

Formatters

[!WARNING] Experimental feature, changes might not follow semver.

Use external formatters to format files that ESLint cannot handle yet (.css, .html, etc). Powered by eslint-plugin-format.

// eslint.config.js
import bclint from 'eslint-conifg-janfr'

export default bclint({
  formatters: {
    /**
     * Format CSS, LESS, SCSS files, also the `<style>` blocks in Vue
     * By default uses Prettier
     */
    css: true,
    /**
     * Format HTML files
     * By default uses Prettier
     */
    html: true,
    /**
     * Format Markdown files
     * Supports Prettier and dprint
     * By default uses Prettier
     */
    markdown: 'prettier'
  }
})

Running npx eslint should prompt you to install the required dependencies, otherwise, you can install them manually:

npm i -D eslint-plugin-format

React

To enable React support, you need to explicitly turn it on:

// eslint.config.js
import bclint from 'eslint-config-janfr'

export default bclint({
  react: true,
})

Running npx eslint should prompt you to install the required dependencies, otherwise, you can install them manually:

npm i -D eslint-plugin-react eslint-plugin-react-hooks eslint-plugin-react-refresh

Svelte

To enable svelte support, you need to explicitly turn it on:

// eslint.config.js
import bclint from 'eslint-config-janfr'

export default bclint({
  svelte: true,
})

Running npx eslint should prompt you to install the required dependencies, otherwise, you can install them manually:

npm i -D eslint-plugin-svelte

Astro

To enable astro support, you need to explicitly turn it on:

// eslint.config.js
import bclint from 'eslint-config-janfr'

export default bclint({
  astro: true,
})

Running npx eslint should prompt you to install the required dependencies, otherwise, you can install them manually:

npm i -D eslint-plugin-astro

UnoCSS

To enable UnoCSS support, you need to explicitly turn it on:

// eslint.config.js
import bclint from 'eslint-config-janfr'

export default bclint({
  unocss: true,
})

Running npx eslint should prompt you to install the required dependencies, otherwise, you can install them manually:

npm i -D @unocss/eslint-plugin

Optional Rules

This config also provides some optional plugins/rules for extended usage.

perfectionist (sorting)

This plugin eslint-plugin-perfectionist allows you to sorted object keys, imports, etc, with auto-fix.

The plugin is installed but no rules are enabled by default.

It's recommended to opt-in on each file individually using configuration comments.

/* eslint perfectionist/sort-objects: "error" */
const objectWantedToSort = {
  a: 2,
  b: 1,
  c: 3,
}
/* eslint perfectionist/sort-objects: "off" */

Type Aware Rules

You can optionally enable the type aware rules by passing the options object to the typescript config:

// eslint.config.js
import bclint from 'eslint-config-janfr'

export default bclint({
  typescript: {
    tsconfigPath: 'tsconfig.json',
  },
})

Lint Staged

If you want to apply lint and auto-fix before every commit, you can add the following to your package.json:

{
  "simple-git-hooks": {
    "pre-commit": "pnpm lint-staged"
  },
  "lint-staged": {
    "*": "eslint --fix"
  }
}

and then

npm i -D lint-staged simple-git-hooks

// to active the hooks
npx simple-git-hooks

View what rules are enabled

Anthony Fu built a visual tool to help you view what rules are enabled in your project and apply them to what files, eslint-flat-config-viewer

Go to your project root that contains eslint.config.js and run:

npx eslint-flat-config-viewer

Versioning Policy

This project follows Semantic Versioning for releases. However, since this is just a config and involves opinions and many moving parts, we don't treat rules changes as breaking changes.

Changes Considered as Breaking Changes

• Node.js version requirement changes
• Huge refactors that might break the config
• Plugins made major changes that might break the config
• Changes that might affect most of the codebases

Changes Considered as Non-breaking Changes

• Enable/disable rules and plugins (that might become stricter)
• Rules options changes
• Version bumps of dependencies

Badge

If you enjoy this code style, and would like to mention it in your project, here is the badge you can use:

[![code style](https://antfu.me/badge-code-style.svg)](https://github.com/antfu/eslint-config)

FAQ

Prettier?

Why we don't use Prettier

Well, you can still use Prettier to format files that are not supported well by ESLint yet, such as .css, .html, etc. See formatters for more details.

dprint?

dprint is also a great formatter that with more abilities to customize. However, it's in the same model as Prettier which reads the AST and reprints the code from scratch. This means it's similar to Prettier, which ignores the original line breaks and might also cause the inconsistent diff. So in general, we prefer to use ESLint to format and lint JavaScript/TypeScript code.

Meanwhile, we do have dprint integrations for formatting other files such as .md. See formatters for more details.

How to format CSS?

You can opt-in to the formatters feature to format your CSS. Note that it's only doing formatting, but not linting. If you want proper linting support, give stylelint a try.

I prefer XXX...

Sure, you can configure and override rules locally in your project to fit your needs. If that still does not work for you, you can always fork this repo and maintain your own.

Credits

• antfu/eslint-config - This config builds upon it

License

MIT License © 2019-PRESENT Anthony Fu