(def $ js/jQuery)
(.each ($ "body") (fn [idx, val]
(.write js/document "In a lambda")))
The Google Closure Compiler munges names of functions so that any function declared in ClojureScript cannot be called from jQuery which means that no jQuery function that takes a callback can be used. And you really want to use GCC because without its dead code removal a simple helloworld.js file takes more than 700kb.