How to use slurp from ClojureScript

slurp.clj

(ns foo.core
  (:refer-clojure :exclude [slurp]))

(defmacro slurp [file]
  (clojure.core/slurp file))

;; In CLJS

(ns bar.core
  (:require [foo.core :include-macros true :refer [slurp]]))

;; This is possible because we can evaluate *Clojure* code at compile time.
(def project-clj 
  (slurp "project.clj"))

I don't understand how this works though, doesn't clojure.core/slurp use java.io stuff? But that's not available in Node.js or the web browser.

@kenfehling because it is a macro it happens at compile time not run time.