react

Airbnb React/JSX Style Guide

A mostly reasonable approach to React and JSX

Table of Contents

1. Basic Rules
2. Class vs React.createClass vs stateless
3. Naming
4. Declaration
5. Alignment
6. Quotes
7. Spacing
8. Props
9. Parentheses
10. Tags
11. Methods
12. Ordering
13. isMounted

Basic Rules

• Only include one React component per file.
  • However, multiple Stateless, or Pure, Components are allowed per file. eslint: react/no-multi-comp.
• Always use JSX syntax.
• Do not use React.createElement unless you're initializing the app from a file that is not JSX.

Class vs React.createClass vs stateless

• If you have internal state and/or refs, prefer class extends React.Component over React.createClass unless you have a very good reason to use mixins. eslint: react/prefer-es6-classreact/prefer-stateless-function

  // badconstListing=React.createClass({// ...render(){return<div>{this.state.hello}</div>;}});// goodclassListingextendsReact.Component{// ...render(){return<div>{this.state.hello}</div>;}}

  And if you don't have state or refs, prefer normal functions (not arrow functions) over classes:

  // badclassListingextendsReact.Component{render(){return<div>{this.props.hello}</div>;}}// bad (relying on function name inference is discouraged)constListing=({ hello })=>(<div>{hello}</div>);// goodfunctionListing({ hello }){return<div>{hello}</div>;}

Naming

• Extensions: Use .jsx extension for React components.

• Filename: Use PascalCase for filenames. E.g., ReservationCard.jsx.

• Reference Naming: Use PascalCase for React components and camelCase for their instances. eslint: react/jsx-pascal-case

  // badimportreservationCardfrom'./ReservationCard';// goodimportReservationCardfrom'./ReservationCard';// badconstReservationItem=<ReservationCard/>;// goodconstreservationItem=<ReservationCard/>;

• Component Naming: Use the filename as the component name. For example, ReservationCard.jsx should have a reference name of ReservationCard. However, for root components of a directory, use index.jsx as the filename and use the directory name as the component name:

  // badimportFooterfrom'./Footer/Footer';// badimportFooterfrom'./Footer/index';// goodimportFooterfrom'./Footer';

Declaration

• Do not use displayName for naming components. Instead, name the component by reference.

  // badexportdefaultReact.createClass({displayName: 'ReservationCard',// stuff goes here});// goodexportdefaultclassReservationCardextendsReact.Component{}

Alignment

• Follow these alignment styles for JSX syntax. eslint: react/jsx-closing-bracket-location

  // bad<FoosuperLongParam="bar"anotherSuperLongParam="baz"/>// good<FoosuperLongParam="bar"anotherSuperLongParam="baz"/>// if props fit in one line then keep it on the same line<Foobar="bar"/>// children get indented normally<FoosuperLongParam="bar"anotherSuperLongParam="baz"><Quux/></Foo>

Quotes

• Always use double quotes (") for JSX attributes, but single quotes for all other JS. eslint: jsx-quotes

Why? JSX attributes can't contain escaped quotes, so double quotes make conjunctions like "don't" easier to type. Regular HTML attributes also typically use double quotes instead of single, so JSX attributes mirror this convention.

```jsx
// bad
<Foo bar='bar' />
// good
<Foo bar="bar" />
// bad
<Foo style={{ left: "20px" }} />
// good
<Foo style={{ left: '20px' }} />
```

Spacing

• Always include a single space in your self-closing tag.

  // bad<Foo/>// very bad<Foo/>// bad<Foo/>// good<Foo/>

• Do not pad JSX curly braces with spaces. eslint: react/jsx-curly-spacing

  // bad<Foobar={baz}/>// good<Foobar={baz}/>

Props

• Always use camelCase for prop names.

  // bad<FooUserName="hello"phone_number={12345678}/>// good<FoouserName="hello"phoneNumber={12345678}/>

• Omit the value of the prop when it is explicitly true. eslint: react/jsx-boolean-value

  // bad<Foohidden={true}/>// good<Foohidden/>

• Always include an alt prop on <img> tags. If the image is presentational, alt can be an empty string or the <img> must have role="presentation". eslint: jsx-a11y/img-has-alt

  // bad<imgsrc="hello.jpg"/>// good<imgsrc="hello.jpg"alt="Me waving hello"/>// good<imgsrc="hello.jpg"alt=""/>// good<imgsrc="hello.jpg"role="presentation"/>

• Do not use words like "image", "photo", or "picture" in <img>alt props. eslint: jsx-a11y/img-redundant-alt

Why? Screenreaders already announce img elements as images, so there is no need to include this information in the alt text.

```jsx
// bad
<img src="hello.jpg" alt="Picture of me waving hello" />
// good
<img src="hello.jpg" alt="Me waving hello" />
```

• Use only valid, non-abstract ARIA roles. eslint: jsx-a11y/aria-role

  // bad - not an ARIA role<divrole="datepicker"/>// bad - abstract ARIA role<divrole="range"/>// good<divrole="button"/>

• Do not use accessKey on elements. eslint: jsx-a11y/no-access-key

Why? Inconsistencies between keyboard shortcuts and keyboard commands used by people using screenreaders and keyboards complicate accessibility.

// bad<divaccessKey="h"/>// good<div/>

• Avoid using an array index as key prop, prefer a unique ID. (why?)

// bad{todos.map((todo,index)=><Todo{...todo}key={index}/>)}// good{todos.map(todo=>(<Todo{...todo}key={todo.id}/>))}

Parentheses

• Wrap JSX tags in parentheses when they span more than one line. eslint: react/wrap-multilines

  // badrender(){return<MyComponentclassName="long body"foo="bar"><MyChild/></MyComponent>;}// goodrender(){return(<MyComponentclassName="long body"foo="bar"><MyChild/></MyComponent>);}// good, when single linerender(){constbody=<div>hello</div>;return<MyComponent>{body}</MyComponent>;}

Tags

• Always self-close tags that have no children. eslint: react/self-closing-comp

  // bad<FooclassName="stuff"></Foo>// good<FooclassName="stuff"/>

• If your component has multi-line properties, close its tag on a new line. eslint: react/jsx-closing-bracket-location

  // bad<Foobar="bar"baz="baz"/>// good<Foobar="bar"baz="baz"/>

Methods

• Use arrow functions to close over local variables.

  functionItemList(props){return(<ul>{props.items.map((item,index)=>(<Itemkey={item.key}onClick={()=>doSomethingWith(item.name,index)}/>))}</ul>);}

• Bind event handlers for the render method in the constructor. eslint: react/jsx-no-bind

Why? A bind call in the render path creates a brand new function on every single render.

```jsx
// bad
class extends React.Component {
onClickDiv() {
// do stuff
}
render() {
return <div onClick={this.onClickDiv.bind(this)} />
}
}
// good
class extends React.Component {
constructor(props) {
super(props);
this.onClickDiv = this.onClickDiv.bind(this);
}
onClickDiv() {
// do stuff
}
render() {
return <div onClick={this.onClickDiv} />
}
}
```

• Do not use underscore prefix for internal methods of a React component.

  // badReact.createClass({_onClickSubmit(){// do stuff},// other stuff});// goodclassextendsReact.Component{onClickSubmit(){// do stuff}// other stuff}

• Be sure to return a value in your render methods. eslint: require-render-return

  // badrender(){(<div/>);}// goodrender(){return(<div/>);}

Ordering

• Ordering for class extends React.Component:

1. optional static methods
2. constructor
3. getChildContext
4. componentWillMount
5. componentDidMount
6. componentWillReceiveProps
7. shouldComponentUpdate
8. componentWillUpdate
9. componentDidUpdate
10. componentWillUnmount
11. clickHandlers or eventHandlers like onClickSubmit() or onChangeDescription()
12. getter methods for render like getSelectReason() or getFooterContent()
13. Optional render methods like renderNavigation() or renderProfilePicture()
14. render

• How to define propTypes, defaultProps, contextTypes, etc...

  importReact,{PropTypes}from'react';constpropTypes={id: PropTypes.number.isRequired,url: PropTypes.string.isRequired,text: PropTypes.string,};constdefaultProps={text: 'Hello World',};classLinkextendsReact.Component{staticmethodsAreOk(){returntrue;}render(){return<ahref={this.props.url}data-id={this.props.id}>{this.props.text}</a>}}Link.propTypes=propTypes;Link.defaultProps=defaultProps;exportdefaultLink;

• Ordering for React.createClass: eslint: react/sort-comp

1. displayName
2. propTypes
3. contextTypes
4. childContextTypes
5. mixins
6. statics
7. defaultProps
8. getDefaultProps
9. getInitialState
10. getChildContext
11. componentWillMount
12. componentDidMount
13. componentWillReceiveProps
14. shouldComponentUpdate
15. componentWillUpdate
16. componentDidUpdate
17. componentWillUnmount
18. clickHandlers or eventHandlers like onClickSubmit() or onChangeDescription()
19. getter methods for render like getSelectReason() or getFooterContent()
20. Optional render methods like renderNavigation() or renderProfilePicture()
21. render

isMounted

• Do not use isMounted. eslint: react/no-is-mounted

Why? isMounted is an anti-pattern, is not available when using ES6 classes, and is on its way to being officially deprecated.

Translation

This JSX/React style guide is also available in other languages:

• Chinese (Simplified): JasonBoy/javascript
• Polish: pietraszekl/javascript
• Korean: apple77y/javascript

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