> efficiently update just the changed portions
Since actually applying each change to the real DOM is too slow, the only way to efficiently update is to batch changes and then apply the delta to the actual DOM.
That means we need to keep track of some state, namely the previously applied state and the current goal state, which you then compare.
Now, you may have noticed that we've just independently invented the concept of diffing. And the extra state that needed to be tracked can be given a spiffy name, like "virtual DOM", since it's like the DOM, but not the real thing.
So, I'm quite unconvinced by Lit-html's claim that they are able to efficiently mutate the DOM without using a vDOM anywhere.
Either their method is not efficient (for example it falls over for rapid updates), or there is a data structure under the hood that is analogous to a vDOM, even if they prefer to give that data structure a different name.
