Comment by jbritton

The Reddit example is about two different design choices. The DOM is a tree of state that needs to stay in sync with your app state. So how to make that happen without turning your code into a mess. The old Reddit had to first construct the DOM and then for every state change, determine what DOM nodes need to change, find them and update them. Knowing what needs to change gets ugly in a lot of apps. The other alternative is to realize that constructing a DOM from any arbitrary state is pretty much the same as constructing it from initial state. But now you don’t have to track what DOM nodes must change on every state change. This is a massive reduction in code complexity. I will grant that there is something similar to the “expression” problem. Every time there is a new state element introduced it may affect the creation of every node in the DOM. As opposed to every time a UI element is added it may affect every state transition. The first Reddit can be fast, but you have to manage all the updates. The second is slow, but easier to develop. I’m not sure going any lower solves any of that. The React version can be made more efficient through intelligent compilers that are at better at detecting change and doing updates. The React model allows for tooling optimizations. These might well beat hand written changes. The web has complexity also of client/server with long delays and syncing client/server and DOM state, and http protocol. Desktop apps and game engines don’t have these problems.