Shadow DOM and custom styling

So I've read this article and from what I understand, each native browser widget is actually a combination of basic elements, styling and scripts. This begs the question - if they are consisted of basic building blocks, does that mean that there is a way of customizing them through JavaScript? And I don't mean in the replacement sort of way, as some JavaScript libraries/plugins do - simply 开发者_运维技巧by accessing their "Shadow DOM" properties and adding some CSS styles to them, for example. Also, this page has some use cases, but nothing practical.

Anyone ever tried anything like this? Is it possible at all? Downsides?

Thanks.

My main concern would be that the implementations of the shadow DOM would be different between browsers and then you are basically back to needing some sort of library to deal with it. I'm not sure if that is the case, but its worth considering. Also, given that there are so many widget libraries available and that is the standard way of handling most of these issues, is it worth taking on a whole new set of unknown issues instead of just working with known elements?