JavaScript Standard Style

One JavaScript Style Guide to Rule Them All

No decisions to make. No .eslintrc, .jshintrc, or .jscsrc files to manage. It just works.

This module saves you (and others!) time in two ways:

• No configuration. The easiest way to enforce consistent style in your project. Just drop it in.
• Catch style errors before they're submitted in PRs. Saves precious code review time by eliminating back-and-forth between maintainer and contributor.

Install with:

npm install standard

The Rules

• 2 spaces – for indentation
• Single quotes for strings – except to avoid escaping
• No unused variables – this one catches tons of bugs!
• No semicolons – It's fine. Really!
• Never start a line with (, [, or `
  • This is the only gotcha with omitting semicolons – automatically checked for you!
  • More details
• Space after keywords if (condition) { ... }
• Space after function name function name (arg) { ... }
• Always use === instead of == – but obj == null is allowed to check null || undefined.
• Always handle the node.js err function parameter
• Always prefix browser globals with window – except document and navigator are okay
  • Prevents accidental use of poorly-named browser globals like open, length, event, and name.
• And more goodness – give standard a try today!

To get a better idea, take a look at a sample file written in JavaScript Standard Style. Or, check out one of the thousands of projects that use standard!

Table of Contents

• Install
• Usage
  • What you might do if you're clever
  • Badge
  • Text editor plugins
• FAQ
  • Why would I use JavaScript Standard Style?
  • I disagree with rule X, can you change it?
  • But this isn't a real web standard!
  • Is there an automatic formatter?
  • How do I ignore files?
  • How do I hide a certain warning?
  • I use a library that pollutes the global namespace. How do I prevent "variable is not defined" errors?
  • Can I use a custom JS parser for bleeding-edge ES next support?
  • Can I use a JavaScript language variant, like Flow?
  • Can you make rule X configurable?
  • What about Web Workers?
  • What about Mocha, Jasmine, QUnit, etc?
  • Is there a Git pre-commit hook?
  • How do I make the output all colorful and pretty?
  • I want to contribute to standard. What packages should I know about?
• Node.js API
  • standard.lintText(text, [opts], callback)
  • standard.lintFiles(files, [opts], callback)
• IRC channel
• License

Install

The easiest way to use JavaScript Standard Style to check your code is to install it globally as a Node command line program. To do so, simply run the following command in your terminal (flag -g installs standard globally on your system, omit it if you want to install in the current working directory):

npm install standard --global

Or, you can run this command to install standard locally, for use in your module:

npm install standard --save-dev

Node.js and npm are required to run the preceding commands.

Usage

After you've installed standard, you should be able to use the standard program. The simplest use case would be checking the style of all JavaScript files in the current working directory:

$ standard
Error: Use JavaScript Standard Style
  lib/torrent.js:950:11: Expected '===' and instead saw '=='.

You can optionally pass in a directory (or directories) using the glob pattern. Be sure to quote paths containing glob patterns so that they are expanded by standard instead of your shell:

$ standard "src/util/**/*.js" "test/**/*.js"

Note: by default standard will look for all files matching the patterns: **/*.js, **/*.jsx.

What you might do if you're clever

1. Add it to package.json

{
  "name": "my-cool-package",
  "devDependencies": {
    "standard": "*"
  },
  "scripts": {
    "test": "standard && node my-tests.js"
  }
}

2. Check style automatically when you run npm test

$ npm test
Error: Use JavaScript Standard Style
  lib/torrent.js:950:11: Expected '===' and instead saw '=='.

3. Never give style feedback on a pull request again!

Badge

Use this in one of your projects? Include one of these badges in your readme to let people know that your code is using the standard style.

[![Standard - JavaScript Style Guide](https://cdn.rawgit.com/feross/standard/master/badge.svg)](https://github.com/feross/standard)

[![Standard - JavaScript Style Guide](https://img.shields.io/badge/code%20style-standard-brightgreen.svg)](http://standardjs.com/)

Text editor plugins

First, install standard. Then, install the appropriate plugin for your editor:

Sublime Text

Using Package Control, install SublimeLinter and SublimeLinter-contrib-standard.

For automatic formatting on save, install StandardFormat.

Atom

Install linter-js-standard.

For automatic formatting, install standard-formatter. For snippets, install standardjs-snippets.

Vim

Install Syntastic and add this line to .vimrc:

let g:syntastic_javascript_checkers = ['standard']

For automatic formatting on save, add these two lines to .vimrc:

autocmd bufwritepost *.js silent !standard --fix %
set autoread

Emacs

Install Flycheck and check out the manual to learn how to enable it in your projects.

Brackets

Search the extension registry for "Standard Code Style".

Visual Studio Code

Install vscode-standardjs. (Includes support for automatic formatting.)

For JS snippets, install: vscode-standardjs-snippets. For React snippets, install vscode-react-standard.

WebStorm/PhpStorm

Both WebStorm and PhpStorm can be configured for Standard Style.

FAQ

Why would I use JavaScript Standard Style?

The beauty of JavaScript Standard Style is that it's simple. No one wants to maintain multiple hundred-line style configuration files for every module/project they work on. Enough of this madness!

This module saves you time in two ways:

• No configuration. The easiest way to enforce consistent style in your project. Just drop it in.
• Catch style errors before they're submitted in PRs. Saves precious code review time by eliminating back-and-forth between maintainer and contributor.

Adopting standard style means ranking the importance of code clarity and community conventions higher than personal style. This might not make sense for 100% of projects and development cultures, however open source can be a hostile place for newbies. Setting up clear, automated contributor expectations makes a project healthier.

I disagree with rule X, can you change it?

No. The whole point of standard is to avoid bikeshedding about style. There are lots of debates online about tabs vs. spaces, etc. that will never be resolved. These debates just distract from getting stuff done. At the end of the day you have to 'just pick something', and that's the whole philosophy of standard -- its a bunch of sensible 'just pick something' opinions. Hopefully, users see the value in that over defending their own opinions.

But this isn't a real web standard!

Of course it's not! The style laid out here is not affiliated with any official web standards groups, which is why this repo is called feross/standard and not ECMA/standard.

The word "standard" has more meanings than just "web standard" :-) For example:

• This module helps hold our code to a high standard of quality.
• This module ensures that new contributors follow some basic style standards.

Is there an automatic formatter?

Yes! You can use standard --fix to automatically fix most issues automatically.

standard --fix is built into standard (since v8.0.0) for maximum convenience. Lots of problems are fixable, but some errors, like forgetting to handle the error in node-style callbacks, must be fixed manually.

To save you time, standard outputs a message ("Run standard --fix to automatically fix some problems.") when it detects problems that can be fixed automatically.

How do I ignore files?

The paths node_modules/**, *.min.js, bundle.js, coverage/**, hidden files/folders (beginning with .), and all patterns in a project's root .gitignore file are automatically ignored.

Sometimes you need to ignore additional folders or specific minified files. To do that, add a standard.ignore property to package.json:

"standard": {
  "ignore": [
    "**/out/",
    "/lib/select2/",
    "/lib/ckeditor/",
    "tmp.js"
  ]
}

How do I hide a certain warning?

In rare cases, you'll need to break a rule and hide the warning generated by standard.

JavaScript Standard Style uses eslint under-the-hood and you can hide warnings as you normally would if you used eslint directly.

To get verbose output (so you can find the particular rule name to ignore), run:

$ standard --verbose
Error: Use JavaScript Standard Style
  routes/error.js:20:36: 'file' was used before it was defined. (no-use-before-define)

Disable all rules on a specific line:

file = 'I know what I am doing' // eslint-disable-line

Or, disable only the "no-use-before-define" rule:

file = 'I know what I am doing' // eslint-disable-line no-use-before-define

Or, disable the "no-use-before-define" rule for multiple lines:

/* eslint-disable no-use-before-define */
console.log('offending code goes here...')
console.log('offending code goes here...')
console.log('offending code goes here...')
/* eslint-enable no-use-before-define */

I use a library that pollutes the global namespace. How do I prevent "variable is not defined" errors?

Some packages (e.g. mocha) put their functions (e.g. describe, it) on the global object (poor form!). Since these functions are not defined or required anywhere in your code, standard will warn that you're using a variable that is not defined (usually, this rule is really useful for catching typos!). But we want to disable it for these global variables.

To let standard (as well as humans reading your code) know that certain variables are global in your code, add this to the top of your file:

/* global myVar1, myVar2 */

If you have hundreds of files, adding comments to every file can be tedious. In these cases, you can add this to package.json:

{
  "standard": {
    "globals": [ "myVar1", "myVar2" ]
  }
}

Can I use a custom JS parser for bleeding-edge ES next support?

Before you use a custom parser, consider whether the added complexity in your build process is worth it.

standard supports custom JS parsers. To use a custom parser, install it from npm (example: npm install babel-eslint) and add this to your package.json:

{
  "standard": {
    "parser": "babel-eslint"
  }
}

If you're using standard globally (you installed it with -g), then you also need to install babel-eslint globally with npm install babel-eslint -g.

Can I use a JavaScript language variant, like Flow?

Before you use a custom JS language variant, consider whether the added complexity in your build process (and effort required to get new contributors up-to-speed) is worth it.

standard supports ESLint plugins. Use one of these to transform your code into valid JavaScript before standard sees it. To use a custom parser, install it from npm (example: npm install eslint-plugin-flowtype) and add this to your package.json:

{
  "standard": {
    "parser": "babel-eslint",
    "plugins": [
      "flowtype"
    ]
  }
}

If you're using standard globally (you installed it with -g), then you also need to install eslint-plugin-flowtype globally with npm install eslint-plugin-flowtype -g.

Can you make rule X configurable?

No. The point of standard is to save you time by picking reasonable rules so you can spend your time solving actual problems. If you really do want to configure hundreds of eslint rules individually, you can always use eslint directly.

If you just want to tweak a couple rules, consider using this shareable config and layering your changes on top.

Pro tip: Just use standard and move on. There are actual real problems that you could spend your time solving! :P

What about Web Workers?

Add this to the top of your files:

/* eslint-env serviceworker */

This lets standard (as well as humans reading your code) know that self is a global in web worker code.

What about Mocha, Jasmine, QUnit, etc?

To support mocha in your test files, add this to the beginning of your test files:

/* eslint-env mocha */

Where mocha can be one of jasmine, qunit, phantomjs, and so on. To see a full list, check ESLint's specifying environments documentation. For a list of what globals are available for these environments, check the globals npm module.

Is there a Git pre-commit hook?

Funny you should ask!

#!/bin/sh
# Ensure all javascript files staged for commit pass standard code style
git diff --name-only --cached --relative | grep '\.jsx\?$' | xargs standard
if [ $? -ne 0 ]; then exit 1; fi

Alternatively, overcommit is a Git hook manager that includes support for running standard as a Git pre-commit hook. To enable this, add the following to your .overcommit.yml file:

PreCommit:
  Standard:
    enabled: true

How do I make the output all colorful and pretty?

The built-in output is simple and straightforward, but if you like shiny things, install snazzy:

npm install snazzy

And run:

$ standard --verbose | snazzy

There's also standard-tap, standard-json, standard-reporter, and standard-summary.

Node.js API

standard.lintText(text, [opts], callback)

Lint the provided source text to enforce JavaScript Standard Style. An opts object may be provided:

var opts = {
  fix: false,   // automatically fix problems
  globals: [],  // global variables to declare
  plugins: [],  // eslint plugins
  envs: [],     // eslint environment
  parser: ''    // js parser (e.g. babel-eslint)
}

The callback will be called with an Error and results object:

var results = {
  results: [
    {
      filePath: '',
      messages: [
        { ruleId: '', message: '', line: 0, column: 0 }
      ],
      errorCount: 0,
      warningCount: 0
    }
  ],
  errorCount: 0,
  warningCount: 0
}

standard.lintFiles(files, [opts], callback)

Lint the provided files globs. An opts object may be provided:

var opts = {
  ignore: [],   // file globs to ignore (has sane defaults)
  cwd: '',      // current working directory (default: process.cwd())
  fix: false,   // automatically fix problems
  globals: [],  // global variables to declare
  plugins: [],  // eslint plugins
  envs: [],     // eslint environment
  parser: ''    // js parser (e.g. babel-eslint)
}

The callback will be called with an Error and results object (same as above).

IRC channel

Join us in #standard on freenode.

Contribute

Contributions are welcome! Check out the issues or the PRs, and make your own if you want something that you don't see there.

I want to contribute to standard. What packages should I know about?

• standard - this repo
  • standard-engine - cli engine for arbitrary eslint rules
  • eslint-config-standard - eslint rules for standard
  • eslint-config-standard-jsx - eslint rules for standard (JSX)
  • eslint-plugin-standard - custom eslint rules for standard (not part of eslint core)
  • eslint - the linter that powers standard
• snazzy - pretty terminal output for standard
• standard-www - code for http://standardjs.com
• semistandard - standard, with semicolons (if you must)

There are also many editor plugins, a list of npm packages that use standard, and an awesome list of packages in the standard ecosystem.

License

MIT. Copyright (c) Feross Aboukhadijeh.