It throws the following:

Uncaught Error: Objects are not valid as a React child (found: object with keys {key, val, __hash, cljs$lang$protocol_mask$partition0$, cljs$lang$protocol_mask$partition1$}). If you meant to render a collection of children, use an array instead.

Strange, I'm definitely doing something wrong here, if I copy the definition of $ locally it works. oO

(defn $$
  "Create a new React element from a valid React type.
  Example:
  

"
  [type & args]
  (let [?p (first args)
        ?c (rest args)
        native? (or (keyword? type)
                    (string? type)
                    (:native (meta type)))
        type' (if (keyword? type)
                (name type)
                type)]
    (println ?p (map? ?p))
    (if (map? ?p)
      (apply create-element
             type'
             (if native?
               (impl.props/-dom-props ?p)
               (impl.props/-props ?p))
             ?c)
      (apply create-element
             type'
             nil
             args))))

;; now works oO
($$ "div" (style) "hello")

You can read about it here https://github.com/lilactown/helix/blob/master/docs/creating-elements.md#dynamic-props

the fix is to do

($ "div {& (style)} "hello")

the definition you copied is of the CLJS function form, not the macro form. When you call ($ ,,,) CLJS chooses the macro first. if you pass the $ as a value, like (apply $ ,,,) then it will use the function that you copied, which does handle dynamic props but is slower.

Got it! Thanks for clarifying

for sure! interested to see what your experiments result in 🙂