Javascript doesn't allow (yet) for conditionally importing modules. This won't work:

if (useBootstrap) {
   import 'bootstrap';
}

but importing css files isn't really using javascript, right? There's a preprocessor that reads the css locatation and creates a stylesheet link. So might it be possible for this to be conditional? I'm thinking of the case where only one theme is loaded.

import 'bootstrap/dist/css/bootstrap.min.css';
if (darkTheme) {
   import 'bootstrap-dark.min.css';
}
// or
import `bootstrap/dist/css/bootstrap-${theme}.min.css`;

I imagine that this isn't easy to support, because the preprocessing happens before the javascript is executed. So brainstorming, perhaps a conditional import?

import_if( 'bootstrap-dark.min.css', useDarkTheme);

Of course, that doesn't feel right, but I figured I'd ask in case there's a way.