anchor.diff:                  Seq.distinct obs
                   |> Seq.toList)
           let checkedView = View.Map (List.exists (fun x -> x = item)) rvi
  -        let checkedAttr =
  -            Attr.DynamicPred "checked" checkedView (View.Const "checked")
           let attrs =
               [
                   Attr.Create "type" "checkbox"
                   Attr.Create "name" (Var.GetId chk |> string)
                   Attr.Create "value" (Fresh.Id ())
  -                checkedAttr
  +                Attr.DynamicProp "checked" checkedView
               ] @ (List.ofSeq attrs) |> Attr.Concat
           let el = DU.CreateElement "input"
           let onClick (x: DomEvent) =
  
positive.code:         let attrs =
              Attr.Concat [
                  yield! attrs
                  yield Attr.DynamicPred "checked" chk.View (View.Const "checked")
              ]
          Doc.Elem el attrs Doc.Empty
  
  
negative.code:         let el = DU.CreateElement "input"
          el.AddEventListener("click", (fun (x : DomEvent) -> Var.Set var value), false)
          let predView = View.Map (fun x -> x = value) var.View
          let valAttr = Attr.DynamicProp "checked" predView
          let (==>) k v = Attr.Create k v
          let attr =
              [
  