How to mount styles inside shadow root using cssinjs/jss

This is what my web component looks like, it is a web component that renders a react app that contains material-ui styles.

import * as React from 'react';
import { render } from 'react-dom';
import { StylesProvider, jssPreset } from '@material-ui/styles';
import { create } from 'jss';

import { App } from '@myApp/core';

class MyWebComponent extends HTMLElement {
  connectedCallback() {
    const shadowRoot = this.attachShadow({ mode: 'open' });
    const mountPoint = document.createElement('span');
    const reactRoot = shadowRoot.appendChild(mountPoint);
    const jss = create({
      ...jssPreset(),
      insertionPoint: reactRoot
    });

    render(
      <StylesProvider jss={jss}>
        <App />
      </StylesProvider>,
      mountPoint
    );
  }
}
customElements.define('my-web-commponent', MyWebComponent);

Setting the insertionPoint on jss to the actual react root inside the shadow root will tell jss to insert those styles inside that shadow root.


Using https://github.com/Wildhoney/ReactShadow to create shadow dom (you could also do it by hand as shown in previous answer), I created a small WrapperComponent that encapsulates the logic.

import root from 'react-shadow';
import {jssPreset, StylesProvider} from "@material-ui/styles";
import {create} from 'jss';
import React, {useState} from "react"

const WrappedJssComponent = ({children}) => {
  const [jss, setJss] = useState(null);
  
  function setRefAndCreateJss(headRef) {
    if (headRef && !jss) {
      const createdJssWithRef = create({...jssPreset(), insertionPoint: headRef})
      setJss(createdJssWithRef)
    }
  }
  
  return (
    <root.div>
      <head>
        <style ref={setRefAndCreateJss}></style>
      </head>
      {jss &&
      <StylesProvider jss={jss}>
        {children}
      </StylesProvider>
      }
    
    </root.div>
  )
}

export default WrappedJssComponent

Then you just need to Wrap your app, or the part of your app you want to shadow inside <WrappedJssComponenent><YourComponent></YourComponent></WrappedJssComponenent>.

Be careful, some of the material-UI component won't work as usual (I had some trouble with

  • ClickAwayListener, maybe because it uses the parent dom, did not investigate more than that to be honest.
  • Popper, and everything that will try to use document.body as container will not have access to jss defined in shadow node. You should give an element inside the shadow dom as container.