Is this doing a full re-render on each change? Having not seen the state management piece... but could be nice for progressive enhancement modules in a server-rendered app. I've done similar in JS.
Nope! It doesn't visit each node like vdom. VDOM visits every virtual node. lit-html looks at only the expressions. That's where a lot of the speed/performance comes from
zeptime's correct. lit-html places markers in the HTML where the expressions are. Then it renders the HTML once, and updates the expressions directly. That's how it avoids a full re-render and avoids building am in-memory VDOM and doing any diffing.