Floating navbar with only a single css property changed (thanks to the magic of reagent, a clojurescript interface to react)

navbar.cljs

;; I think this will work.  It's extracted from a working version here: 
;; https://github.com/paultopia/stdio  (mostly in the nav namespace)
;; so if you try this and it doesn't work, I probably left something off, feel free to go to the original.

(ns navbar.core
  (:require [reagent.core :as r :refer [render atom]]))

(defn loren [reps]
  (apply str (take reps (repeat "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do
      eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim
      ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut
      aliquip ex ea commodo consequat. Duis aute irure dolor in
      reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla
      pariatur. Excepteur sint occaecat cupidatat non proident, sunt in
      culpa qui officia deserunt mollit anim id est laborum."))))

(def scrollpos (atom 0))

(defn update-scroll []
  (reset! scrollpos (.-pageYOffset js/window)))

(defn track-scroll []
  (.addEventListener js/window "scroll" update-scroll))

(defn crazyfloat [sp]
  (cond
    (< sp 30) "static"
    :else "fixed"))

(defn navbar []
  [:div {:style {:position (crazyfloat @scrollpos)}}
   ; components containing navbar items go here
   ])

(defn das-page []
  [:div
    [navbar]
    [:p (loren 10]])

(track-scroll)

(render [das-page] (.getElementById js/document "app"))

This is an insane hack to avoid writing CSS. Uses reagent to implement a floating top navbar from scratch without changing more than a single CSS property. The strategy is just to hook an event listener on scroll that updates a ratom containing the y-axis position, and then make the position property of the div containing the navbar depend on that.

Which is nutty, and makes the navbar appear to jump around a teensy bit, but is so so so so much nicer than having to fight with css to get the elements under the navbar positioned correctly with respect to it.

Looks simple, already playing with it :)