@zinserjan/eslint-config-react

v0.1.0

Published

3 years ago

A set of opinionated ESLint rules tailored for React Components

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zinserjan

eslint-config-react

A mostly reasonable approach to React and JSX based on the great Airbnb React/JSX Style Guide

Installation

npm install --save-dev @zinserjan/eslint-config-react

.eslintrc

{
  "extends": [
     "@zinserjan/eslint-config-react"
  ]
}

Basic Rules

Only include one React component per file.
- However, multiple Stateless, or Pure, Components are allowed per file. eslint: react/no-multi-comp.
Avoid usage of React.createClass
Always use JSX syntax.
Always add type definition for properties
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. 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

Filename: Use PascalCase for filenames. E.g., ReservationCard.js.

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.js should have a reference name of ReservationCard.

// bad - Component defined in index.js
import Footer from "./Footer";
import Footer from "./Footer/index";

// good
import Footer from "./footer/Footer";

// good - without folder
import Footer from "./Footer";

Higher-order Component Naming: Use a composite of the higher-order component's name and the passed-in component's name as the displayName on the generated component. For example, the higher-order component withFoo(), when passed a component Bar should produce a component with a displayName of withFoo(Bar).

Why? A component's displayName may be used by developer tools or in error messages, and having a value that clearly expresses this relationship helps people understand what is happening.

```jsx
// 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 for different purposes.

Why? People expect props like style and className to mean one specific thing. Varying this API for a subset of your app makes the code less readable and less maintainable, and may cause bugs.

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

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

Declaration

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

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

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

// good
function ReservationCard() {
}

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. eslint: jsx-quotes

Why? 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. eslint: no-multi-spaces, react/jsx-space-before-closing
```
// 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.

```jsx
// bad
<div accessKey="h" />

// good
<div />
```

Avoid using an array index as key prop, prefer a unique ID. (why?) eslint: react/no-array-index-key

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

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

Do not pass CSS classes & styles between custom components. This rule only applies to Components (e.g. <Foo />) and not DOM nodes (e.g. <div />). eslint: react/forbid-component-props

Why? These add lots of complexity to Components.

```jsx
// bad
<Hello className="foo" />
<Hello style={{color: "red"}} />

// good
<Hello name="Joe" />
<div className="foo" />
<div style={{color: "red"}} />
```

Always define propTypes accurately for all props and avoid PropTypes.any, PropTypes.array, PropTypes.object. eslint: react/forbid-prop-types

// bad
class Component extends React.Component {
  ...
}
Component.propTypes = {
  a: React.PropTypes.any,
  r: React.PropTypes.array,
  o: React.PropTypes.object
};

class Component extends React.Component {
  static propTypes = {
    a: React.PropTypes.any,
    r: React.PropTypes.array,
    o: React.PropTypes.object
  };
  render() {
    return <div />;
  }
}

// good
class Component extends React.Component {
  ...
}
Component.propTypes = {
  a: React.PropTypes.string,
  r: React.PropTypes.arrayOf(PropTypes.string),
  o: React.PropTypes.shape({
    id: PropTypes.number.isRequired
  })
};

class Component extends React.Component {
  static propTypes = {
    a: React.PropTypes.string,
    r: React.PropTypes.arrayOf(PropTypes.string),
    o: React.PropTypes.shape({
      id: PropTypes.number.isRequired
    })
  };
  render() {
    return <div />;
  }
}

Always define explicit defaultProps for all non-required props. eslint: react/require-default-props

Why? propTypes are a form of documentation, and providing defaultProps means the reader of your code doesn’t have to assume as much. In addition, it can mean that 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 }) {
  return <div>{foo}{bar}</div>;
}
SFC.propTypes = {
  foo: PropTypes.number.isRequired,
  bar: PropTypes.string,
};
SFC.defaultProps = {
  bar: "",
  children: null,
};

Refs

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

// bad
<Foo
  ref="myRef"
/>

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

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} />
  }
}

// good with class properties
class extends React.Component {
  onClickDiv = () => {
    // do stuff
  };

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

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

Why? Underscore prefixes are sometimes used as a convention in other languages to denote privacy. But, unlike those languages, there is no native support for privacy in JavaScript, everything is public. Regardless of your intentions, adding underscore prefixes to your properties does not actually make them private, and any property (underscore-prefixed or not) should be treated as being public. See issues #1024, and #490 for a more in-depth discussion.

```jsx
// 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: react/require-render-return
```
// bad
render() {
  (<div />);
}

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

Control structures

React doesn't provide helpers for control structures out of the box and just allows the usage of native javascript helpers like ternary operator or Array.map. There is no if/else or each statement like in Handlebars. To eliminate this lack we use JSX Control Statements which gives us some of the missing helpers :)

Conditional rendering. eslint: jsx-control-statements/jsx-if-require-condition
```
<div>
  <If condition={true}>
    <span>IfBlock</span>
  </If>
</div>
```

Conditional rendering with alternatives eslint: jsx-control-statements/jsx-choose-not-empty, jsx-control-statements/jsx-when-require-condition, jsx-control-statements/jsx-otherwise-once-last

<div>
  <Choose>
    <When condition={test1}>
      <span>IfBlock</span>
    </When>
    <When condition={test2}>
      <span>ElseIfBlock</span>
      <span>Another ElseIfBlock</span>
      <span>...</span>
    </When>
    <Otherwise>
      <span>ElseBlock</span>
    </Otherwise>
  </Choose>
</div>

Loops via native [].map

// single element
<div>
  {[1,2,3].map((n) => {
    return <p>{n}</p>
  })}
</div>

// multiple elements
<div>
  {[1,2,3].map((n) => {
    return ([
      <h3></h3>, // note the comma
      <p></p>
    ]);
  })}
</div>

Ordering

Ordering for class extends React.Component:

optional type annotations (flowtype)
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...

without class properties

```jsx
import React, { Component, PropTypes } from "react";

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

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

class Link extends 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;
```

with class properties

```jsx
import React, { Component, PropTypes } from "react";

export default class Link extends Component {

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

  static defaultProps = {
    text: "Hello World",
  };

  static methodsAreOk() {
    return true;
  }

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

`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.

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