// app.js
import '../scss/index.scss';
import AnComponent from './components/AnComponent/index';

// ./components/AnComponent/index.js
import './src/scss/index.scss';

export default class AnComponent Component {
    render() {
        return (
            <div class="component">
               I am a example component
            </div>
        );
    }
}

// ../scss/index.scss
body{
    background-color:red;
}

// ./components/AnComponent/src/scss/index.scss
body{
    background-color:green;
}