       nav.on 'affixed.bs.affix', affixResize
       nav.on 'affixed-top.bs.affix', affixResize
       undefined
-    , [ref.current]
+    , []
 
     <nav className="contents" ref={ref}>
       <ul className="nav contents">

    slider.current.on 'change', (e) =>
      messageHistory.set message._id, diffs[e.newValue]
    messageHistory.set message._id, diffs[index]
  , [message._id, message.creator, message.created, input.current]

  <div className="historySlider">
    <input type="text" ref={input}/>

  useEffect ->
    id2dom[message._id] = ref.current
    -> delete id2dom[message._id]
  , [message._id]
  ## Scroll to this message if it's been requested.
  useEffect ->
    if scrollToLater == message._id
