@iamstarkov/react-jss-theming-plus NPM

React integration of JSS

There is a number of benefits when using react-jss instead of JSS directly:

Theming support out of the box.
Lazy evaluation - sheet is created only when component will mount.
Auto attach/detach - sheet will be rendered to the dom when component is about to mount and will be removed when no element needs it.
A sheet gets shared between all elements.
You want to use it with React Hot Loader.

Also you may need this module if you build a big application where leaving all styles in the DOM or compiling all styles at once may have a performance overhead or you are going to hit IE limits.

Install

npm install --save react-jss

Usage

You can use it as a higher-order component to inject JSS. It can act both as a simple wrapping function and as a ES7 decorator.

React JSS wraps your React component and injects props.classes and props.sheet, which is a regular JSS StyleSheet, as props into your component. This is a common pattern that is used for composition in React instead of mixins, and works equally well with old-style createClass classes, as well as the ES6 classes.

Because JSS class names are namespaced by default, you will need to reach into this.props.classes to get their real names. For example, if you define a button class in your JSS stylesheet, its real name will be available as props.classes.button.

By default react-jss comes with jss and presets.

Basic

import React from 'react'
import injectSheet from 'react-jss'

const styles = {
  button: {
    background: props => props.color
  },
  label: {
    fontWeight: 'bold'
  }
}

const Button = ({classes, children}) => (
  <button className={classes.button}>
    <span className={classes.label}>
      {children}
    </span>
  </button>
)

export default injectSheet(styles)(Button)

Theming

import { ThemeProvider, withTheme } from 'react-jss';

Idea is simple. You define theme object. You pass it to ThemeProvider which in turn passes it to context, then you use withTheme to map it back from context to components props. After that you may change your theme, and all your components will get new theme automatically.

Under the hood react-jss uses unified CSSinJS theming solution for React. You can find detailed docs in its repo.

In your app you will need ThemeProvider:

It has theme prop which should be an object or function:
- If it is an Object and used in a root ThemeProvider then it's intact and being passed down the react tree.
- If it is Object and used in a nested ThemeProvider then it's being merged with theme from a parent ThemeProvider and passed down the react tree.
- If it is Function and used in a nested ThemeProvider then it's being applied to the theme from a parent ThemeProvider. If result is an Object it will be passed down the react tree, throws otherwise.
ThemeProvider as every other component can render only single children, because it uses React.Children.only in render, which returns the only child in children. Throws otherwise.
Read more about ThemeProvider in theming's documentation.

import React from 'react'
import { ThemeProvider } from 'react-jss'
import { Button } from './components'

const theme = {
  colorPrimary: 'green',
};

const App = () => {
  <ThemeProvider theme={theme}>
    <Button>I am a button with green background</Button>
  </ThemeProvider>
}

export default App;

In your components you will need withTheme. It is a Higher-order Component which takes a single React.Component and maps a theme object from context to props. Read more about withTheme in theming's documentation.

import React from 'react'
import injectSheet, { withTheme } from 'react-jss'

const styles = {
  button: {
    background: props => props.theme.colorPrimary
  },
  label: {
    fontWeight: 'bold'
  }
}

const Button = ({classes, children}) => (
  <button className={classes.button}>
    <span className={classes.label}>
      {children}
    </span>
  </button>
)

export default withTheme(injectSheet(styles)(Button))

Server-side rendering

import {renderToString} from 'react-dom/server'
import {SheetsRegistryProvider, SheetsRegistry} from 'react-jss'
import MyApp from './MyApp'

export default function render(req, res) {
  const sheets = new SheetsRegistry()

  const body = renderToString(
    <SheetsRegistryProvider registry={sheets}>
      <MyApp />
    </SheetsRegistryProvider>
  )

  // any instances of `injectStyle` within `<MyApp />` will have gotten `sheets`
  // from `context` and added their style sheets to it by now.

  return res.send(renderToString(
    <html>
      <head>
        <style type="text/css">
          {sheets.toString()}
        </style>
      </head>
      <body>
        {body}
      </body>
    </html>
  ))
}

Reuse same StyleSheet in different Components

Sometimes you may need to reuse the same StyleSheet in different components, without generating new styles for each. You can pass StyleSheet instance to the injectSheet? function instead of styles object.

import React, {Component} from 'react'
import injectSheet, { jss } from 'react-jss'

const sheet = jss.createStyleSheet({
  button: {
    color: 'red'
  }
})

@injectSheet(sheet)
class Button extends Component {
  render() {
    const {classes} = this.props
    return <button className={classes.button}></button>
  }
}

classNames helper

You can use classNames together with JSS same way you do it with global CSS.

import classNames from 'classnames'

const Component = ({classes, children, isActive}) => (
  <div
    className={classNames({
      [classes.normal]: true,
      [classes.active]: isActive
    })}>
    {children}
  </div>
)

The inner component

const InnerComponent = () => null
const StyledComponent = injectSheet(styles, InnerComponent)
console.log(StyledComponent.InnerComponent) // Prints out the inner component.

Custom setup

If you want to specify a jss version and plugins to use, you should create your own jss instance, setup plugins and create a injectSheet function which has your jss version bound.

import {create as createJss} from 'jss'
import {create as createInjectSheet} from 'react-jss'
import vendorPrefixer from 'jss-vendor-prefixer'

const jss = createJss()
jss.use(vendorPrefixer())

export const injectSheet = createInjectSheet(jss)

You can also access the Jss instance being used by default.

import {jss} from 'react-jss'

Decorators

Beware that decorators are stage-2 proposal, so there are no guarantees that decorators will make its way into language specification. Do not use it in production. Use it at your own risk and only if you know what you are doing.

You will need babel-plugin-transform-decorators-legacy.

import React, {Component} from 'react'
import injectSheet from 'react-jss'

const styles = {
  button: {
    backgroundColor: 'yellow'
  },
  label: {
    fontWeight: 'bold'
  }
}

@injectSheet(styles)
export default class Button extends Component {
  render() {
    const {classes, children} = this.props
    return (
      <button className={classes.button}>
        <span className={classes.label}>
          {children}
        </span>
      </button>
    )
  }
}