React Guidelines

Imports

A common way to sort the imports in the file is by their source: external, absolute, relative separated by an empty line. Each of those groups can be sorted by line length, but that's not super important.

import React, { useState } from 'react'
import { useTranslation } from 'next-i18next'

import Nav from 'components/layout/Nav'
import Layout from 'components/layout/Layout'

import SimpleForm from './SimpleForm'
import styles from './advanced.module.scss'

File structure

Inherits AirBnb naming convention https://github.com/airbnb/javascript/tree/master/react#naming

Use PascalCase for React components and camelCase for their instances

Naming convention react components

Pascal cased file names src/components/GenericForm.tsx

export default function GenericForm() {}

Filename and default component of the file should have the same name.

Naming convention non react components

Camel cased file names src/utils/hooks/useUser.ts

Naming convention folders

Lowercase kebab cased folders src/components/common/password-reset/ResetForm.tsx

Naming convention pages

Lowercase kebab cased files located in src/pages/sample-page.tsx which correspond to /sample-page url.

Types

The common convention is that the main type of the component's props is called after the component itself with suffix -Props. Prop types of AdvancedForm becomes AdvancedFormProps.

type AdvancedFormProps = React.PropsWithChildren({
  title?: string
  age?: number
})

export default function AdvancedForm({ title = 'Nice', children, age }: AdvancedFormProps) {
  return (
    <div title={title} data-age={age}>
      {children}
    </div>
  )
}

Components

Preferred export style 🌞

• Nice IDE support and readability

RegisterPage.tsx

export default function RegisterPage() {
  return <div>page</div>
}

Alternative export styles

• Named function

  ⛅ Allows attaching static props to the function

  function RegisterPage() {
    return <div>page</div>
  }
  
  Register.getInitialProps = async (ctx) => {
    return { stars: 128 }
  }
  
  export default RegisterPage

• Const arrow function

  🌞 Nice for locally defined components

  const RegisterForm = () => <form>page</form>
  
  export default function RegisterPage() {
    return <RegisterForm />
  }

  ⛅ Okay for default exports, but not preferred

  const RegisterPage = () => <form>page</form>
  
  export default RegisterPage

• Unnamed arrow function ⛈️

  Discouraged

  https://github.com/yannickcr/eslint-plugin-react/blob/master/docs/rules/display-name.md

  export default () => <div>page</div>

• Class components ⛈️

  Discouraged as hooks cannot be used inside the class components

  class Page extends React.Component {
    render() {
      return <div>page</div>
    }
  }

Styles

There are three common ways to style a component:

Styles using the <Box /> component

Single component that inherits all sizing props from MUI https://material-ui.com/system/basics/#all-inclusive

🌞 Nice for quick layouts that should follow the theme

<Box component="nav" px={5} mt={2}>
  <a>{t('nav.forgottenPassword')}</p>
</Box>

⛅Not the best for custom scenarios with more than _six props passed to it. Use hooks instead

⛅ Not nice when the children have clear nesting structure of more than _three levels. Use hooks or scss instead

<Box component="nav" px={5} pb={12} mt={2} mb={4} lineHeight={2} letterSpacing={none} fontSize={20}>
  <Box component="span" px={5} pb={12} mt={2} mb={4} lineHeight={2} letterSpacing={none} fontSize={17}>
    <a>{t('nav.forgottenPassword')}</p>
  </Box>
  <Box component="span" px={5} pb={12} mt={2} mb={4} lineHeight={2} letterSpacing={none} fontSize={13}>
    <a>{t('nav.forgottenPassword')}</p>
  </Box>
</Box>

Styles using useStyles() hook

🌞 Nice for very specific styling that leverages theme methods and props

const useStyles = makeStyles((theme) =>
  createStyles({
    pageTitle: {
      display: 'flex',
      flexDirection: 'column',
      alignItems: 'center',
      padding: theme.spacing(4),
      margin: theme.spacing(5, 3, 4),
      color: theme.palette.secondary.main,
      backgroundColor: theme.palette.primary.main,
      '&:hover': {
        color: theme.palette.secondary.dark,
      },
    },
    // ...
  }),
)

export default function SomeBox() {
  const classes = useStyles()
  return (
    <Box className={classes.pageTitle}>
      <p>{t('nav.forgottenPassword')}</p>
    </Box>
  )
}

⛅ Too verbose for simple use cases, if it contains less than 2 css rules. Use Box instead

⛅ Not the best when dealing with styling of deep nested structures within the same component. Use scss instead

Styles using SCSS files

Next.js supports SCSS out of the box. Read more at https://nextjs.org/docs/basic-features/built-in-css-support#sass-support

File convention is based on a suffix .module.scss (ex. about.module.scss)

🌞 Nice when dealing with complex nested structures that are scoped in a single component. When dealing with sub-components we're not sure if some of the rules will be left unused.

@import 'styles/variables';

.page {
  color: $text-color;

  .nav {
    background-color: $nav-color;

    a {
      text-decoration: none;
      text-transform: uppercase;
    }
  }
}

import styles from './about.module.scss'

<Box className={styles.page}>
  <p>{t('nav.forgottenPassword')}</p>
</Box>

⛅ Too verbose for simple use cases, if it contains less than 2 css rules in a dedicated file. Use Box instead

@import 'styles/variables';

a {
  text-decoration: none;
}

⛈️ Cannot use theme support or theme variables Use hook instead