My first thought for the React example would be to replace the CSS files with styled-components, emotion, or one of the other copycat CSS-in-JS libs with an identical base API.

    import { css } from 'emotion';

    const WhateverComponent = () => (
      <div className={css`
        background-color: green;
        height: 100%;
      `} />
    );

    export default WhateverComponent;

...or...

    import styled from 'react-emotion';

    const WhateverComponent = ({ className }) => (
      <div className={className} />
    );

    export default styled(WhateverComponent)`
      background-color: green;
      height: 100%;
    `;

...or...

    import styled from 'react-emotion';

    const BigGreenBox = styled('div')`
      background-color: green;
      height: 100%;
    `

    const WhateverComponent = () => (
      <BigGreenBox />
    );

    export default WhateverComponent;