This is better than this

This:

      changeSize: function(size) {
        $$('div.what_it_looks_like').invoke("hide");
        $(size).show();
      }
    

is better than this.

      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;
        }
      }
    

And I'm still a Javascript n00b.