Airbnb React/JSX Style Guide

A mostly reasonable approach to React and JSX

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-class react/prefer-stateless-function

// bad
const Listing = React.createClass({
  // ...
  render() {
    return <div>{this.state.hello}</div>;
  }
});

// good
class Listing extends React.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:

// bad
class Listing extends React.Component {
  render() {
    return <div>{this.props.hello}</div>;
  }
}

// bad (relying on function name inference is discouraged)
const Listing = ({ hello }) => (
  <div>{hello}</div>
);

// good
function Listing({ 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

// bad
import reservationCard from './ReservationCard';

// good
import ReservationCard from './ReservationCard';

// bad
const ReservationItem = <ReservationCard />;

// good
const reservationItem = <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:
```
// bad
import Footer from './Footer/Footer';

// bad
import Footer from './Footer/index';

// good
import Footer from './Footer';
```

Declaration

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

// bad
export default React.createClass({
  displayName: 'ReservationCard',
  // stuff goes here
});

// good
export default class ReservationCard extends React.Component {
}

Alignment

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

// bad
<Foo superLongParam="bar"
     anotherSuperLongParam="baz" />

// good
<Foo
  superLongParam="bar"
  anotherSuperLongParam="baz"
/>

// if props fit in one line then keep it on the same line
<Foo bar="bar" />

// children get indented normally
<Foo
  superLongParam="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
<Foo bar={ baz } />

// good
<Foo bar={baz} />
```

Props

Always use camelCase for prop names.

// bad
<Foo
  UserName="hello"
  phone_number={12345678}
/>

// good
<Foo
  userName="hello"
  phoneNumber={12345678}
/>

Omit the value of the prop when it is explicitly true. eslint: react/jsx-boolean-value
```
// bad
<Foo
  hidden={true}
/>

// good
<Foo
  hidden
/>
```

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
<img src="hello.jpg" />

// good
<img src="hello.jpg" alt="Me waving hello" />

// good
<img src="hello.jpg" alt="" />

// good
<img src="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
<div role="datepicker" />

// bad - abstract ARIA role
<div role="range" />

// good
<div role="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
<div accessKey="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

// bad
render() {
  return <MyComponent className="long body" foo="bar">
           <MyChild />
         </MyComponent>;
}

// good
render() {
  return (
    <MyComponent className="long body" foo="bar">
      <MyChild />
    </MyComponent>
  );
}

// good, when single line
render() {
  const body = <div>hello</div>;
  return <MyComponent>{body}</MyComponent>;
}

Methods

Use arrow functions to close over local variables.

function ItemList(props) {
  return (
    <ul>
      {props.items.map((item, index) => (
        <Item
          key={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.

// bad
React.createClass({
  _onClickSubmit() {
    // do stuff
  },

  // other stuff
});

// good
class extends React.Component {
  onClickSubmit() {
    // do stuff
  }

  // other stuff
}

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

// bad
render() {
  (<div />);
}

// good
render() {
  return (<div />);
}

Ordering

Ordering for class extends React.Component:

optional static methods
constructor
getChildContext
componentWillMount
componentDidMount
componentWillReceiveProps
shouldComponentUpdate
componentWillUpdate
componentDidUpdate
componentWillUnmount
clickHandlers or eventHandlers like onClickSubmit() or onChangeDescription()
getter methods for render like getSelectReason() or getFooterContent()
Optional render methods like renderNavigation() or renderProfilePicture()
render

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

import React, { PropTypes } from 'react';

const propTypes = {
  id: PropTypes.number.isRequired,
  url: PropTypes.string.isRequired,
  text: PropTypes.string,
};

const defaultProps = {
  text: 'Hello World',
};

class Link extends React.Component {
  static methodsAreOk() {
    return true;
  }

  render() {
    return <a href={this.props.url} data-id={this.props.id}>{this.props.text}</a>
  }
}

Link.propTypes = propTypes;
Link.defaultProps = defaultProps;

export default Link;

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

displayName
propTypes
contextTypes
childContextTypes
mixins
statics
defaultProps
getDefaultProps
getInitialState
getChildContext
componentWillMount
componentDidMount
componentWillReceiveProps
shouldComponentUpdate
componentWillUpdate
componentDidUpdate
componentWillUnmount
clickHandlers or eventHandlers like onClickSubmit() or onChangeDescription()
getter methods for render like getSelectReason() or getFooterContent()
Optional render methods like renderNavigation() or renderProfilePicture()
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

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README.md

README.md

Airbnb React/JSX Style Guide

Table of Contents

Basic Rules

Class vs `React.createClass` vs stateless

Naming

Declaration

Alignment

Quotes

Spacing

Props

Parentheses

Tags

Methods

Ordering

`isMounted`

Translation

Files

README.md

Latest commit

History

README.md

File metadata and controls

Airbnb React/JSX Style Guide

Table of Contents

Basic Rules

Class vs React.createClass vs stateless

Naming

Declaration

Alignment

Quotes

Spacing

Props

Parentheses

Tags

Methods

Ordering

isMounted

Translation

Class vs `React.createClass` vs stateless

`isMounted`