Completed percentage

gistfile1.txt

function completedPercentage(notification)
{
  var completed = new Notification(notification).completedChecklistItem();
  var num_complete = completed.checklist().items().find(function(item)
  {
    if(item.isComplete())
      return item;
    else
      return false;
  }).length();
  
  var num_items = completed.checklist().items().length();
  completed.checklist().card().setCustomFieldValue("Percentage Complete",new Number((num_complete*100)/num_items).toFixed(2));
  
}