javascript/react

Airbnb React/JSX Style Guide

A mostly reasonable approach to React and JSX

Table of Contents

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

Basic Rules

• Only include one React component per file.
• 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

• Use class extends React.Component unless you have a very good reason to use mixins.

eslint rules: react/prefer-es6-class.

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

// good
class Listing extends React.Component {
  render() {
    return <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 rules: react/jsx-pascal-case.

  // bad
  const reservationCard = require('./ReservationCard');
  
  // good
  const ReservationCard = require('./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
  const Footer = require('./Footer/Footer.jsx')
  
  // bad
  const Footer = require('./Footer/index.jsx')
  
  // good
  const Footer = require('./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 rules: react/jsx-closing-bracket-location.

```javascript
// 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"
>
  <Spazz />
</Foo>
```

Quotes

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

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.

eslint rules: jsx-quotes.

```javascript
// 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 />
  

Props

• Always use camelCase for prop names.

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

Parentheses

• Wrap JSX tags in parentheses when they span more than one line.

eslint rules: react/wrap-multilines.

```javascript
/// 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>;
}
```

Tags

• Always self-close tags that have no children.

eslint rules: react/self-closing-comp.

```javascript
// bad
<Foo className="stuff"></Foo>

// good
<Foo className="stuff" />
```

• If your component has multi-line properties, close its tag on a new line.

eslint rules: react/jsx-closing-bracket-location.

```javascript
// bad
<Foo
  bar="bar"
  baz="baz" />

// good
<Foo
  bar="bar"
  baz="baz"
/>
```

Methods

• 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
  });
  

Ordering

• Ordering for class extends React.Component:

1. constructor
2. optional static methods
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...

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:

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

eslint rules: react/sort-comp.

isMounted

• Do not use isMounted.

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

eslint rules: react/no-is-mounted.

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