defonce would preserve app state after hot reloads

[qrthey]

create-cljs-app/template/src/app/hello.cljs

Line 11 in 7e99103

(def click-count (r/atom 0))

In clojurescript the state ratom would typically be defined with defonce instead of with def. Doing so would ensure that the state of the application is kept when new changes are saved (be it in cljs files or stylesheets).