React/JSX Style Guide…!

A best & 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.
• react/forbid-prop-types will allow arrays and objects only if it is explicitly noted what array and object contains, using arrayOf, objectOf, or shape.

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 Conventions for React App (PascalCase vs camelCase)

• Extensions: Use .jsx extension for React components. eslint: react/jsx-filename-extension
• 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';

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 withFooAlok(), when passed a component Bar should produce a component with a displayName of withFooAlok(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.

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

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

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

  WithFooAlok.displayName = `withFooAlok(${wrappedComponentName})`;
  return WithFooAlok;
}

Props Naming: Avoid using DOM component props 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.

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

// bad
<MyComponent className="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
});
// good
export default class ReservationCard extends React.Component {
// stuff goes here
}

Alignment in component (.jsx file) <Alok />

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

Quotes “very important”/’very important’

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

Why? 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

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

Props (… / <Alok companyName=”GL” />)

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
<Alok
  hidden={true}
/>
// good
<Alok
  hidden
/>
// good
<Alok 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

Why? Screen readers 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" />

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

Why? Not using a stable ID is an anti-pattern because it can negatively impact performance and cause issues with component state.

We don’t recommend using indexes for keys if the order of items may change.

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

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

Refs in React [ref={(ref) => { this.myRef = ref; }}]

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/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>;
}

Tags </>

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

// bad
<Foo variant="stuff"></Foo>
// good
<Foo variant="stuff" />

If your component has multiline 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. It is handy when you need to pass additional data to an event handler. Although, make sure they do not massively hurt performance, in particular when passed to custom components that might be PureComponents, because they will trigger a possibly needless rerender every time.

function ItemList(props) {
  return (
    <ul>
      {props.items.map((item, index) => (
        <Item
          key={item.key}
          onClick={(event) => { doSomethingWith(event, 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. Do not use arrow functions in class fields, because it makes them challenging to test and debug, and can negatively impact performance, and because conceptually, class fields are for data, not logic.

// 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.

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.

// 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 />);
}

That’s all from my side…!!