Possible leak in heavy app
javascript is garbage collected, unless you're making huge(tens of MB of XML/JSON) data transfers every couple of seconds and keep references to that data, there should be "no memory leak" unless the browser is doing a lousy job.

I would put "items" array as global variable so that with each request, you overwrite it, in this way, old data will be discarded, i.e.

// moved globally
var items = [];
function list_stuff(data, type, where, order) 
{
  // try to parse data as JSON
  try 
  {
    items = jQuery.parseJSON(data);
    var index;
    var item;
    for ( index = 0; index &lt; items.length; index++ )
    {
      item = items[index];
      // do something with "item"
    }
  }
  catch(e)
  {
    // handle error here
  }
}