There is a failure to process (require 'cljs.js) when in an --init file for the browser REPL. I haven't found any other namespace that this fails with (for example, clojure.set doesn't exhibit this).
It works fine with Node:
Add an explicit -e with require prior to the -i:
This is an odd workaround because, if you use it, you still need the require in the foo.cljs file.