React and JSX

The Airbnb React/JSX style guide covers how to write components consistently — from file structure and naming conventions to prop handling, event binding, and component ordering.

Basic rules

Only include one React component per file.

Multiple stateless (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.
arrays and objects prop types are only allowed when they explicitly describe their contents using arrayOf, objectOf, or shape. eslint: react/forbid-prop-types

Class vs `React.createClass` vs stateless

When a component has internal state or refs, prefer class extends React.Component over React.createClass. eslint: react/prefer-es6-class, react/prefer-stateless-function

Good
Bad

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

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

When a component has no state or refs, prefer a normal named function over a class or anonymous arrow function.

// 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>;
}

Mixins

Do not use mixins.

Mixins introduce implicit dependencies, cause name clashes, and cause snowballing complexity. Most use cases for mixins can be accomplished in better ways via components, higher-order components, or utility modules.

Naming

Extensions: Use .jsx for React component files. eslint: react/jsx-filename-extension Filename: Use PascalCase for filenames — for example, 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 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';

Higher-order component naming: Use a composite of the HOC name and the passed-in component’s name as the displayName on the generated component. For example, withFoo(Bar).

A component’s displayName may be used by developer tools or in error messages. A clear, composite name helps people understand the relationship.

// bad
export default function withFoo(WrappedComponent) {
  return function WithFoo(props) {
    return <WrappedComponent {...props} foo />;
  }
}

// good
export default function withFoo(WrappedComponent) {
  function WithFoo(props) {
    return <WrappedComponent {...props} foo />;
  }

  const wrappedComponentName = WrappedComponent.displayName
    || WrappedComponent.name
    || 'Component';

  WithFoo.displayName = `withFoo(${wrappedComponentName})`;
  return WithFoo;
}

Props naming: Avoid using DOM component prop names (like style or className) for different purposes.

// bad
<MyComponent style="fancy" />

// bad
<MyComponent className="fancy" />

// good
<MyComponent variant="fancy" />

Declaration

Do not use displayName for naming components. Name the component by reference instead.

Good
Bad

export default class ReservationCard extends React.Component {
}

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

Alignment

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

For conditional rendering:

// bad
{showButton &&
  <Button />
}

// bad
{
  showButton &&
    <Button />
}

// good
{showButton && (
  <Button />
)}

// good
{showButton && <Button />}

// good
{someReallyLongConditional
  && anotherLongConditional
  && (
    <Foo
      superLongParam="bar"
      anotherSuperLongParam="baz"
    />
  )
}

// good
{someConditional ? (
  <Foo />
) : (
  <Foo
    superLongParam="bar"
    anotherSuperLongParam="baz"
  />
)}

Quotes

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

Regular HTML attributes also typically use double quotes instead of single, so JSX attributes mirror this convention.

// 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. eslint: no-multi-spaces, react/jsx-tag-spacing

// bad
<Foo/>

// very bad
<Foo                 />

// bad
<Foo
 />

// good
<Foo />

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

Good
Bad

<Foo bar={baz} />

<Foo bar={ baz } />

Props

Always use camelCase for prop names, or PascalCase if the prop value is a React component.

Good
Bad

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

<Foo
  UserName="hello"
  phone_number={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/alt-text

// 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

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

// 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

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 stable ID. eslint: react/no-array-index-key

Using an array index as a key is an anti-pattern because it can negatively impact performance and cause issues with component state.

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

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

Always define explicit defaultProps for all non-required props.

propTypes are a form of documentation, and providing defaultProps means the reader of your code doesn’t have to assume as much. It can also mean your code can omit certain type checks.

// bad
function SFC({ foo, bar, children }) {
  return <div>{foo}{bar}{children}</div>;
}
SFC.propTypes = {
  foo: PropTypes.number.isRequired,
  bar: PropTypes.string,
  children: PropTypes.node,
};

// good
function SFC({ foo, bar, children }) {
  return <div>{foo}{bar}{children}</div>;
}
SFC.propTypes = {
  foo: PropTypes.number.isRequired,
  bar: PropTypes.string,
  children: PropTypes.node,
};
SFC.defaultProps = {
  bar: '',
  children: null,
};

Use spread props sparingly — you’re more likely to pass unnecessary props down to components.

Acceptable exceptions include HOCs that proxy down props and hoist propTypes, or spreading objects with known, explicit props (for example, in test setup).

When spreading props, filter out anything irrelevant to the wrapped component.

// bad
render() {
  const { irrelevantProp, ...relevantProps } = this.props;
  return <WrappedComponent {...this.props} />
}

// good
render() {
  const { irrelevantProp, ...relevantProps } = this.props;
  return <WrappedComponent {...relevantProps} />
}

Refs

Always use ref callbacks. eslint: react/no-string-refs

Good
Bad

<Foo
  ref={(ref) => { this.myRef = ref; }}
/>

<Foo
  ref="myRef"
/>

Parentheses

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

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

// good
render() {
  return (
    <MyComponent variant="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 when you need to pass additional data to an event handler.

function ItemList(props) {
  return (
    <ul>
      {props.items.map((item, index) => (
        <Item
          key={item.key}
          onClick={(event) => { doSomethingWith(event, item.name, index); }}
        />
      ))}
    </ul>
  );
}

Arrow functions in event handlers create a new function on every render. Avoid passing them to custom components that extend PureComponent, as they will trigger a rerender on every cycle.

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

A bind call in the render path creates a brand new function on every render. Do not use arrow functions in class fields — class fields are for data, not logic, and arrow functions there are challenging to test and debug.

// bad
class extends React.Component {
  onClickDiv() {
    // do stuff
  }

  render() {
    return <div onClick={this.onClickDiv.bind(this)} />;
  }
}

// very bad
class extends React.Component {
  onClickDiv = () => {
    // do stuff
  }

  render() {
    return <div onClick={this.onClickDiv} />
  }
}

// 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.

JavaScript has no native support for privacy. Adding underscore prefixes does not actually make properties private — everything is public regardless of your naming.

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

  // other stuff
});

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

  // other stuff
}

Always return a value in your render methods. eslint: react/require-render-return

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

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

Ordering

For class extends React.Component, use this order:

optional static methods
constructor
getChildContext
componentWillMount
componentDidMount
componentWillReceiveProps
shouldComponentUpdate
componentWillUpdate
componentDidUpdate
componentWillUnmount
event handlers starting with handle, like handleSubmit() or handleChangeDescription()
event handlers starting with on, like onClickSubmit() or onChangeDescription()
getter methods for render, like getSelectReason() or getFooterContent()
optional render methods, like renderNavigation() or renderProfilePicture()
render

Here is how to define propTypes, defaultProps, and contextTypes:

import React from 'react';
import PropTypes from 'prop-types';

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;

For React.createClass, use this order: eslint: react/sort-comp

displayName
propTypes
contextTypes
childContextTypes
mixins
statics
defaultProps
getDefaultProps
getInitialState
getChildContext
componentWillMount
componentDidMount
componentWillReceiveProps
shouldComponentUpdate
componentWillUpdate
componentDidUpdate
componentWillUnmount
click/event handlers 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

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

Introduction

Core Language

Advanced Patterns

Code Style

Specialized Guides

React and JSX

React and JSX

Basic rules

Class vs `React.createClass` vs stateless

Mixins

Naming

Declaration

Alignment

Quotes

Spacing

Props

Refs

Parentheses

Tags

Methods

Ordering

`isMounted`

Build docs developers (and LLMs) love

Introduction

Core Language

Advanced Patterns

Code Style

Specialized Guides

​React and JSX

​Basic rules

​Class vs React.createClass vs stateless

​Mixins

​Naming

​Declaration

​Alignment

​Quotes

​Spacing

​Props

​Refs

​Parentheses

​Tags

​Methods

​Ordering

​isMounted

Build docs developers (and LLMs) love

React and JSX

Basic rules

Class vs `React.createClass` vs stateless

Mixins

Naming

Declaration

Alignment

Quotes

Spacing

Props

Refs

Parentheses

Tags

Methods

Ordering

`isMounted`