gistfile1.coffee

ko.extenders.progressiveArray = (target, opts = {}) ->
  target.progressive = _.extend({
    batchSize: 10
  }, opts)

  # Utility function for adding without value mutation events
  target.add ?= (item) -> target().push(item)
  target.clear ?= () -> target([])

  target.updateProgressive = (items) ->
    status = $.Deferred()
    target.clear()

    addItems = (items) ->
      remaining = items.slice(target.progressive.batchSize)
      items = items.slice(0, target.progressive.batchSize)

      for item in items
        target.add(item)

      target.valueHasMutated()

      if remaining.length > 0
        requestAnimationFrame(() -> addItems(remaining))
      else
        status.resolve()

    addItems(items)
    return status

  return target