create.js.erb

if ($('repliesContainer')) {
  var containerElement = $('repliesContainer');
  var highlightEffect = function() {
    var newElement = containerElement.getChildren('div').getLast();
    newElement.setStyle('color', '#ffa');
  };
  new Request.HTML({
    url: '<%= instruction_instruction_item_reply_path(:id => @reply.id) %>',
    append: $(containerElement),
    onSuccess: highlightEffect
  }).get();
} else {
  new MUI.notification('Reply saved.');
}