code: function singleMarker(map, popupCreator, unclickable) {
  	  mapPointerStyle(map);return function (t, d, p, u) {
  	    if (t === 1) {
  	      if (markerStore.markers[0]) {
  	        markerStore.removeMarker(markerStore.markers[0]);
  	      }
  	      createAndAddMarker(map, d, popupCreator, u);
  	    }
  	  };
  	}
docs: TODO: discuss the various function parameters