What doe this syntax (.-body ...) mean in clojurescript/reagent?

Question

This is from reagent docs.

(defn mountit []
  (r/render-component [childcaller]
                      (.-body js/document))) ; (.-body) what is this?

Answer 1

That is JavaScript interop and accesses the body property of document, same as document.body in JavaScript. See: http://cljs.info/cheatsheet/. So the Reagent component will be mounted at the body element of the page.