Show HN: How HN's upvote link works

Each link has an anchor tag like this:

  <a href="vote?for=4156127&amp;dir=up&amp;by=asto&amp;auth=12345&amp;whence=%6e%65%77%73" onclick="return vote(this)" id="up_4156127">
  <img vspace="3" hspace="2" border="0" src="http://ycombinator.com/images/grayarrow.gif">
  </a>

The vote function looks like this:

  function vote(node) {
  var v = node.id.split(/_/);   // {'up', '123'}
  var item = v[1]; 

  // hide arrows
  byId('up_'   + item).style.visibility = 'hidden';
  byId('down_' + item).style.visibility = 'hidden';

  // ping server
  var ping = new Image();
  ping.src = node.href;

  return false; // cancel browser nav

byId is getElementById. I don't know about you guys but I thought this was pretty neat!