code: function(yOrdering) {
  
          this.compare = yOrdering ? 
              OpenLayers.ElementsIndexer.IndexingMethods.Z_ORDER_Y_ORDER :
              OpenLayers.ElementsIndexer.IndexingMethods.Z_ORDER_DRAWING_ORDER;
  
          this.clear();
      }
docs: APIMethod: initialize
  Create a new indexer with
  
  Parameters:
  yOrdering - {Boolean} Whether to use y-ordering.