how to check if a clojure object is a byte-array?

The way I used to do this until now was creating an array of that type and testing for it's class. To prevent creating an unnecessary instance every time, make a function that closes over the class of that particular array type.

(defn test-array
  [t]
  (let [check (type (t []))]
    (fn [arg] (instance? check arg))))

(def byte-array?
  (test-array byte-array))

=> (byte-array? (byte-array 8))
true

=> (byte-array? [1 2 3])
false

Mobyte's example seems a lot simpler though, and it seems I'll have some refactoring to do where I used this :)

(defn bytes? [x]
  (if (nil? x)
    false
    (= (Class/forName "[B")
       (.getClass x))))

Update. The same question has been already asked here Testing whether an object is a Java primitive array in Clojure. And google gives exactly that page on your question "how to check if a clojure object is a byte-array?" ;)