div1000.cljs

(require '[clojure.string :as string])

(defn f
  [n]
  (let [s (str n)]
    (js/parseFloat
      (if-let [[[_ a b]] (re-seq #"(\d*)\.(\d*)" (if (string/starts-with? s "0") (subs s 1) s))]
        (let [al (- (count a) 3)]
          (if (> al 0) 
            (str (subs a 0 al) "." (subs a al) b)
            (str (apply str "0." (repeat (- al) "0")) (when-not (= "0" a) a) b)))
        (let [nl (- (count s) 3)]
          (str (subs s 0 nl) "." (subs s nl)))))))