Follow the original Airbnb JavaScript Style Guide.

This document describes only those rules which we decided to extend, to override or to add.

Other Style Guides:

• React

TODO:

• Make it as a shareable cards (Twitter, FB and other Social Media)
• Apply https://google.github.io/styleguide/javascriptguide.xml

1. Comparison Operators & Equality
2. Comments
3. Semicolons
4. Lines
5. Naming Conventions
6. Imports
7. Packages
8. Type Casting & Coercion
9. Template Strings
10. Objects
11. Classes & Constructors
12. Unsorted Yet

Extends: Section 15

• 1.1 Ternaries should not be as a part of expression, only whole expression.

  TODO: find or make ESLint rule for this

  Why? The following example demonstrate how it could be misunderstood.

  // bad
  const query = { 'forward_url': '/' }
  const targetURL = 'https://qwe.com/auth?' + (typeof query === 'string') ? query : JSON.stringify(query)
  
  // Uncaught TypeError: split is not a function
  // because type of targetURL is Object
  const partsOfURL = targetURL.split('?')
  
  
  // may be
  const query = { 'forward_url': '/' }
  const queryString = typeof query === 'string' ? query : JSON.stringify(query)
  const targetURL = 'https://qwe.com/auth?' + queryString
  
  
  // good
  const query = { 'forward_url': '/' }
  const queryString = (typeof query === 'string') ? query : JSON.stringify(query)
  const targetURL = 'https://qwe.com/auth?' + queryString

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Extends: Section 18

• 2.1 Avoid using obvious comments.

  Why? It makes code harder to read because you can think that here is something else than you see.

  // bad - it duplicates the function name
  
  /**
   * Update hosts
   */
  function updateHosts(list) {
    hosts = list
  }
  
  
  // good - nothing bad is better than something bad
  function updateHosts(list) {
    hosts = list
  }
  
  
  // bad - it duplicates the module path
  import Drawer from 'react-native-drawer'
  
  // Components
  import DrawerMenu from './components/drawer-menu'
  
  
  // good - see the previous "good" explaination
  import Drawer from 'react-native-drawer'
  import DrawerMenu from './components/drawer-menu'
  
  
  // good
  if (!root.isAbstract()) {
    // No need to wrap child nodes of a known concrete type.
    return nextChildren;
  }

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Extends: Section 21

• 3.1 Don't use semicolons, in the presence of excellent automation tools.

  ESLint rule: semi

  Why? Since we always have linting tools we can detect dangerous situations automatically. But this style makes us really faster according to a few years experience.

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• 4.1 80 characters is good. But feel free to use up to 100 characters in a line.

  ESLint rule: max-len

  Why? Almost all developers used to 80 characters. It's a very old practice. Now we have a wide screens and we used to seat a little bit more far from monitor. In this case we can use a bit more characters and code will be still readable.

  Read this and this for more details.

  // bad
  if ((this.props.suggestions.length === 0) && (newProps.suggestions.length > 0) && (newProps.autosuggestValue.length > 0) {
  
    return
  }
  
  // good
  const hasSuggestions = (this.props.suggestions.length === 0)
  const willHaveSuggestions = (newProps.suggestions.length > 0)
  if (hasSuggestions && willHaveSuggestions && (newProps.autosuggestValue.length > 0)) {
    return
  }
  
  // good
  const hasSuggestions = (this.props.suggestions.length === 0)
  const willHaveSuggestions = (newProps.suggestions.length > 0)
  const willHaveAutosuggest = (newProps.autosuggestValue.length > 0)
  if (hasSuggestions && willHaveSuggestions && willHaveAutosuggest) {
    return
  }

• 4.2 Don't use excess empty line

  ESLint rule: no-unexpected-multiline, padded-blocks

  // bad
  const config = loadConfig()
  
  if (config) {
    applyConfig(config)
  }
  
  
  // good
  const config = loadConfig()
  if (config) {
    applyConfig(config)
  }

• 4.3 One empty line before and after function or class declaration.

  ESLint rule: no-unexpected-multiline

  Why? No empty line needed after function or class declaration - if the following line is javascript brackets.

  // bad
  
  const x = 0
  function a() {
    return 1
  }
  const b = () => 2
  
  
  // bad
  
  const x = 0
  class A {
    a() {
      return 1
    }
    b() {
      return 2
    }
  }
  
  
  // good
  
  const x = 0
  
  function a() {
    return 1
  }
  
  const b = () => 2
  
  
  // good
  
  const x = 0
  
  class A {
  
    a() {
      return 1
    }
  
    b() {
      return 2
    }
  }

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Extends: Section 22

• 5.1 Avoid using reduced names.

  Why? It makes code harder to understand. Names are for readability, not to appease a computer algorithm.

  // bad - what does it mean "ref"? referals? references? single reference?
  const ref1 = fetch('/api/books')
  
  
  // good
  const reference1 = fetch('/api/books')

• 5.2 Do not override globals.

  // bad 
  import fetch from './fetch-with-credentials'
  
  // good
  import fetchWithCredentials from './fetch-with-credentials'
  
  // bad
  function alert(message) {
    console.error(message)
  }
  
  // good
  function alertToConsole(message) {
    console.error(message)
  }

• 5.3 Acronyms and initialisms should always be all capitalized.

  Why? Names are for readability, not to appease a computer algorithm.

  // bad
  import SmsContainer from './containers/SmsContainer'
  
  // bad
  const HttpRequests = [
    // ...
  ]
  
  // good
  import SMSContainer from './containers/SMSContainer'
  
  // good
  const HTTPRequests = [
    // ...
  ]
  
  // best
  import TextMessageContainer from './containers/TextMessageContainer'
  
  // best
  const requests = [
    // ...
  ]

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• 6.1 Use the following modules import order:

  • React
  • Relay
  • Redux
  • Tools from node_modules
  • Tools from current repo
  • Other components
  • Any kind of static assets
  • Styles
  • Constants

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• 7.1 Try to avoid using Lodash and Ramda.

  Why? Underscore and Lodash has been made when ES6 has not been so popular. Ramda do not have performance benefits, but being opinionated custom approach increase unnecessary requirements for Developers skills. Besides of that Ramda did not stay "standard de-facto".

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Extends: Section 22

• 8.1 Do not use JavaScript "magic".

  ESLint rule: no-implicit-coercion, no-bitwise

  It makes source code more portable to other languages and available for reading by other developers.

  // bad
  const b = !!a
  
  // bad
  const b = (~a.indexOf('k'))
  
  // bad
  const c = !!d.length
  
  // good
  const b = Boolean(a)
  
  // good
  const b = (a.indexOf('k') >= 0)
  
  // good
  const c = (d.length > 0)

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Extends: Section 6

• 9.1 Don't call function inside template string.

  TODO: find or make ESLint rule for this

  // bad
  const targetURL = `${getHost()}/search/?query=${query}`
  
  
  // good
  const targetHost = getHost()
  const targetURL = `${targetHost}/search/?query=${query}`

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Extends: Section 3

• 10.1 Do not mix expression in one-line objects as assignment.

  TODO: find or make ESLint rule for this

  // bad
  this.setState({ hasErrors: true, route })
  
  
  // bad
  const state = { hasErrors: true, route }
  
  
  // good
  this.setState({ hasErrors, route })
  
  
  // good
  this.setState({ hasErrors: true })
  
  
  // good
  const state = { hasErrors, route }

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Extends: Section 9

• 11.1 Static members should be declared in class body

  TODO: find or make ESLint rule for this

  // bad
  
  Profile.propTypes = {
    classes: PropTypes.object.isRequired,
    handleClick: PropTypes.func,
  }
  
  
  // good
  
  class Profile extends Component {
  
    static propTypes = {
      classes: PropTypes.object.isRequired,
      handleClick: PropTypes.func,
    }
  
    // ...
  }

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• 12.1 Use brackets for expressions.

  TODO: find or make ESLint rule for this

  // bad
  const useSrcKey = _srcKey !== undefined || this._srcKey !== undefined
  const componentAsync = typeof src === 'function' ? src() : import(src)
  const isProduction = process.env['NODE_ENV'] === 'production'
  
  // good
  const useSrcKey = (_srcKey !== undefined) || (this._srcKey !== undefined)
  const componentAsync = (typeof src === 'function') ? src() : import(src)
  const isProduction = (process.env['NODE_ENV'] === 'production')

• 12.2 Use dot syntax only for internal objects.

  TODO: find or make ESLint rule for this

  Seperate importable/exportable JSON data objects and internal runtime objects.

  Also it means - do not mix accessing to values by dot and by string.

  Google Closure Advanced Compilation: Whenever possible, use dot-syntax property names rather than quoted strings. Use quoted string property names only when you don't want Closure Compiler to rename a property at all. For example, to export a property you must use a quoted string. However, for properties used only within your compiled code, use dot syntax.

  // bad
  fetch('/api/users')
    .then(response => response.json())
    .then(json => {
      if (!json.errors) {
        json.data.users.forEach(user => {
          const { id, name } = user
          if (users[id].name !== name) {
            setUserName(id, name)
          }
        })
      }
    })
  
  // bad
  const a = { b: 1 }
  console.log(a['b'])
  
  // bad
  const a = { 'b': 1 }
  console.log(a.b)
  
  // good
  fetch('/api/users')
    .then(response => response.json())
    .then(json => {
      if (!json['errors']) {
        json['data']['users'].forEach(user => {
          const id = user['id']
          const name = user['name']
          if (users[id].name !== name) {
            setUserName(id, name)
          }
        })
      }
    })
    
  // good
  const a = { b: 1 }
  console.log(a.b)
  
  // good
  const a = { 'b': 1 }
  console.log(a['b'])

  It also means you can't rename stringifed keys because they are not in your code base only - in external API, data files, etc.

• 12.3 Don't mix JS and JSX in one line.

  TODO: find or make ESLint rule for this

  // bad
  return <ReferenceLink referenceKey={key} id={ref.id} title={ref.title}/>
  
  
  // bad
  const body = items.map(it => <li>{it.title}</li>)
  
  
  // good
  return (
    <ReferenceLink referenceKey={key} id={ref.id} title={ref.title}/>
  );
  
  
  // good
  const body = items.map(it => (
    <li>{it.title}</li>
  ))
  
  
  // good
  return (
    <References>
      {items.map((it, index) => (
        <ReferenceLink referenceKey={index} id={it['id']} title={it['title']}/>
      ))}
    </References>
  )

• 12.4 Don't mix JSX and Text node in one line.

  TODO: find or make ESLint rule for this

  // bad
  return (
    <Text style={style.openInSafariLink}>Open in Safari</Text>
  )
  
  
  // good
  return (
    <Text style={style.openInSafariLink}>
      Open in Safari
    </Text>
  )
  
  
  // good - if you need a Text node for styling
  return (
    <Text>&nbsp;</Text>
  )

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