Batman.js Even/Odd CSS trick for iterations.

filters.coffee

Batman.mixin Batman.Filters,

  indexOf: (set, iteration) -> set?.toArray().indexOf(iteration)
  isEven:  (input) -> input % 2 == 0

index.html

<ul>
  <li data-foreach-task="tasks"
    data-bind="task.name"
    data-addclass-even="tasks | indexOf task | isEven"></li>
</ul>