<div>
  <button click.trigger="newItems()">new</button>
  <button click.trigger="clearItems()">clear</button>
  Start:
  <button click.trigger="addItemsAtStart(1)">+1</button>
  <button click.trigger="addItemsAtStart(-1)">-1</button>
  <button click.trigger="addItemsAtStart(10)">+10</button>
  <button click.trigger="addItemsAtStart(-10)">-10</button>
  <button click.trigger="addItemsAtStart(100)">+100</button>
  <button click.trigger="addItemsAtStart(-100)">-100</button>
  End:
  <button click.trigger="addI