total-offset.clj

(defprotocol IOffset
  (-offset [x]))

(extend-type js/Element
  IOffset
  (-offset [x]
    [(.-offsetLeft x) (.-offsetTop x)]))

(defprotocol IScroll
  (-scroll [x]))

(extend-type js/Element
  IScroll
  (-scroll [x]
    [(.-scrollLeft x) (.-scrollTop x)]))

(defn addv [v0 v1] (map + v0 v1))

(defn subv [v0 v2] (map - v0 v1))

(defn parent-seq [x]
  (when-let [p (.-offsetParent x)]
    (lazy-seq (cons p (parent-seq p)))))

(defn total-offset [el]
  (let [xs (cons el (parent-seq el))
        vs (map subv (map -offset xs) (map -scroll xs))]
    (reduce addv [0 0] vs)))