Utilise Shadow DOM in React with all the benefits of style encapsulation.

• npm: npm i react-shadow --save
• Heroku: http://react-shadow.herokuapp.com/

By using ReactShadow you have all the benefits of Shadow DOM in React.

import ShadowDOM from 'react-shadow';

export default props => {

    return (
        <ShadowDOM include={['css/core/calendar.css', props.theme]}>
            <h1>Calendar for {props.date}</h1>
        </ShadowDOM>
    );

}

In the above example the h1 element will become the host element with a shadow boundary — and the two defined CSS documents will be fetched and appended.

As the CSS documents are being fetched over the network, the host element will have a className of resolving for you to avoid the dreaded FOIC. Once all of the documents have been attached the className will change to resolved.

Using the resolved class name you could then allow the component to appear once all styles have been applied.

.component {
    opacity: 0;
    transform: scale(.75);
    transition: all .35s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

.component.resolved {
    opacity: 1;
    transform: scale(1);
}

Oftentimes components share the same documents, however only one instance will be fetched due to memoize of the fetchInclude function.

Instead of defining external CSS documents to fetch, you could choose to add all of the component's styles to the component itself by simply embedding a style node in your component. Naturally all styles added this way will be encapsulated within the shadow boundary.

export default props => {

    const styles = `:host { background-color: ${props.theme} }`;

    return (
        <ShadowDOM>
          <div>
            <h1>Calendar for {props.date}</h1>
            <style type="text/css">{styles}</style>
          </div>
        </ShadowDOM>
    );
}

Note: Using inline styles will not combine styles into one style node.