The main benefit of declarative UI frameworks is that they remove the need to manually reconcile changes in state with changes in the representation of that sta

The main benefit of declarative UI frameworks is that they remove the need to manually reconcile changes in state with changes in the representation of that state (with the caveat that it often becomes difficult to do so if the DSL doesn’t cover the behaviour you want). UIs inherently have a hell of a lot of state that is constantly in flux, so it can become very difficult to manage those transitions correctly and efficiently. By providing a description of how an interface should look given some program state, the developer only need be concerned with the flow of data, and the framework can automatically create and apply the delta to update the UI in the most efficient way. For example, there’s no possibility to forget to re-enable a button in that rarely-used code path, because the “enabled” state is derived from the rest of your app state and any changes to that automatically cascade downwards. I’m not saying these things are a silver bullet (and I don’t even really do much UI stuff anymore), but when my job involved frontend web stuff, moving from jQuery to Vue was both an unbelievable jump in both productivity and a massive decrease in UI bugs (and LoC!).