Axept JavaScript Style Guide

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

Comparison Operators & Equality
Comments
Semicolons
Lines
Naming Conventions
Imports
Packages
Type Casting & Coercion
Template Strings
Objects
Classes & Constructors
Unsorted Yet

Comparison Operators & Equality

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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Comments

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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Semicolons

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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Lines

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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Naming Conventions

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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Imports

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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Packages

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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Type Casting & Coercion

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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Template Strings

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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Objects

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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Classes & Constructors

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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Unsorted Yet

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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axept / javascript

Axept JavaScript Style Guide

Contents

Comparison Operators & Equality

Comments

Semicolons

Lines

Naming Conventions

Imports

Packages

Type Casting & Coercion

Template Strings

Objects

Classes & Constructors

Unsorted Yet

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