I’m referring to leakage in the other direction. Think of a lightbox library as a layer over JavaScript’s API. When working with a library you can either use

I’m referring to leakage in the other direction. Think of a lightbox library as a layer over JavaScript’s API. When working with a library you can either use the configuration options provided or just go back down a layer. The space spanned by the configuration options is inevitably smaller than the full space of possibilities you have when working at the JavaScript level, so it’s likely that you have to go back down to JavaScript anyway. That’s why I prefer working with libraries with less friction between the layers over those that try to anticipate a use case but are useless as soon as you need something different. As phzbOx mentioned the Django authentication system is another example.