Show HN: How HN's upvote link works

11 pointsby asto14 lat temu6 comments

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" 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!

2 comments

jgrahamc14 lat temu

Which part did you find neat?

asto14 lat temu

//ping server

Xymak1y14 lat temu

It's an interesting way to not use XMLHttpRequest for Ajax.

Spoom14 lat temu

I'm curious; why didn't they use an AJAX request?

asto14 lat temu

Backward compatibility with really old browsers is all I can think of.

ImJasonH14 lat temu

It's also much less code. It only really works if you don't care about the content of the response, though you could add an onerror handler that would fire on all error cases.