This is better than this

<p>This:</p>

<code><pre>
  changeSize: function(size) {
    $$('div.what_it_looks_like').invoke("hide");
    $(size).show();
  }
</pre></code>


<p>is better than this.</p>

<code><pre>
  changeSize: function(size) {
    switch(size) {
      case 'medium_rectangle' :
        $('medium_rectangle').show();
        $('skyscraper').hide();
        $('leaderboard').hide();
        break;
      case 'skyscraper' :
        $('medium_rectangle').hide();
        $('skyscraper').show();
        $('leaderboard').hide();
        break;
      case 'leaderboard' :
        $('medium_rectangle').hide();
        $('skyscraper').hide();
        $('leaderboard').show();
        break;
    }
  }
</pre></code>

<p>And I'm still a Javascript n00b.</p>