cljs.reader/escape-char

(defn escape-char
  [buffer reader]
  (let [ch (read-char reader)
        mapresult (escape-char-map ch)]
    (if mapresult
      mapresult
      (cond
        (identical? ch \x)
        (->> (read-2-chars reader)
          (validate-unicode-escape unicode-2-pattern reader ch)
          (make-unicode-char))

        (identical? ch \u)
        (->> (read-4-chars reader)
          (validate-unicode-escape unicode-4-pattern reader ch)
          (make-unicode-char))

        (numeric? ch)
        (.fromCharCode js/String ch)

        :else
        (reader-error reader "Unexpected unicode escape \\" ch )))))