JavaScript happiness style ❤️ XOXO

JavaScript happiness style ❤️ XOXO

Enforce strict code style. Never discuss code style on a pull request again!

No decision-making. No .eslintrc, .jshintrc, .jscsrc to manage. It just works!

Uses ESLint underneath, so issues regarding rules should should be opened over there.

  • Tab indentation
  • Semicolons
  • Single-quotes
  • No unused variables
  • Space after keyword if (condition) {}
  • Always === instead of ==

Any of these can be overridden if necessary.

Check out an example and the ESLint rules.

$ npm install --global xo
$ xo --help
    $ xo [<file|glob> ...]
    --init          Add XO to your project
    --compact       Compact output
    --stdin         Validate code from stdin
    --esnext        Enable ES2015 support and rules
    --env           Environment preset  [Can be set multiple times]
    --global        Global variable  [Can be set multiple times]
    --ignore        Additional paths to ignore  [Can be set multiple times]
    --space         Use space indent instead of tabs  [Default: 2]
    --no-semicolon  Prevent use of semicolons
    $ xo
    $ xo index.js
    $ xo *.js !foo.js
    $ xo --esnext --space
    $ xo --esnext --env=node --env=mocha
    Put options in package.json instead of using flags so other tools can read it.

The recommended workflow is to add XO locally to your project and run it with the tests.

Simply run $ xo --init to add XO to your package.json:

    "name": "my-awesome-project",
    "scripts": {
        "test": "mocha"
    "devDependencies": {
        "mocha": "^2.0.0"
    "name": "my-awesome-project",
    "scripts": {
        "test": "xo && mocha"
    "devDependencies": {
        "mocha": "^2.0.0",
        "xo": "^0.5.0"

You can configure some options in XO by putting it in package.json:

    "name": "my-awesome-project",
    "xo": {
        "envs": ["node", "mocha"]

Globals and rules can be configured inline in files.

Type: boolean
Default: false

Enable ES2015 support and linting rules.

Type: array
Default: ['node']

Which environments your code is designed to run in. Each environment brings with it a certain set of predefined global variables.

Type: array

Additional global variables your code accesses during execution.

Type: array

Some paths are ignored by default. Additional ignores can be added here.

Type: boolean, number
Default: false (tab indentation)

Set it to true to get 2-space indentation or specify the number of spaces.

This option exists for pragmatic reasons, but I would strongly recommend you read "Why tabs are superior".

Type: object

Override any of the default rules. See the ESLint docs for more info on each rule.

Please take a moment to consider if you really need to use this option.

Type: boolean
Default: true (semicolons required)

Set it to false to enforce no-semicolon style.

The Standard style is a really cool idea. I too wish we could have one style to rule them all! Unfortunately, they made the mistake of pushing their own style instead of the most popular one. I don't think it's realistic to convert everyone. In contrast, XO is more pragmatic and has no aspiration of being the style. XO does use tabs by default, but everything is configurable if necessary.

XO is based on ESLint. This project started out as just a shareable ESLint config, but it quickly grew out of that. I wanted something even simpler. Just typing xo and be done. No decision-making. No config. I also have some exciting future plans for it. However, you can still get most of the XO benefits while using ESLint directly with the ESLint shareable config.

MIT © Sindre Sorhus