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

⬆ back to top

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; }

⬆ back to top

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.

⬆ back to top

• 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 } }

⬆ back to top

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 = [ // ... ]

⬆ back to top

• 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

⬆ back to top

• 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".

⬆ back to top

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)

⬆ back to top

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}`

⬆ back to top

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 }

⬆ back to top

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, } // ... }

⬆ back to top

• 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> )

⬆ back to top