<div class="heart btn pull-right click-heart peinto-heart-empty" data-is-clicked="false" data-sketch-id="someid"></div>

<div class="poop btn pull-right click-poop peinto-poop-empty" data-is-clicked="false" data-sketch-id="someid"></div>

<div class="voting-box">
    <button class="upvote" ... >Up!</button>
    <button class="downvote" ... >Down!</button>
</div>

function onUpvoteClick(event) {
    var downvoteButton = $(event.target).parent().find('.downvote');
    // do something with the downvote button, eg:
    downvoteButton.css('color', 'red');
}

Item 1
<a class="vote" data-id="1" data-direction="up">Vote Up</a>
<a class="vote" data-id="1" data-direction="down">Vote Down</a>

<br>

Item 2
<a class="vote" data-id="2" data-direction="up">Vote Up</a>
<a class="vote" data-id="2" data-direction="down">Vote Down</a>

$(function() {
  $('a.vote').click(function(e) {
    var id = $(this).data('id');

    //save the vote (via ajax)

    $('a.vote[data-id="' + id + '"]').removeClass('selected');
    $(this).addClass('selected');
  });
});