Style Guide for React application

Style Guide for React application

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.

  • 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 />

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>;
    }

Tags

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

    // bad
    <Foo className="stuff"></Foo>
    
    // good
    <Foo className="stuff" />
  • If your component has multi-line properties, close its tag on a new line. eslint: react/jsx-closing-bracket-location

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

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

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

⬆ back to top

About the author

Hey, I'm Tarun, a software engineer, writer, and open-sourcerer. I publish articles and tutorials about modern JavaScript, design, and programming.

Get the newsletterBuy me a coffee

tkssharma