要素
                      var output;
                      if (geom instanceof ol.geom.Polygon) {
                          output = formatArea(/** @type {ol.geom.Polygon} */(geom));//面积值
                          tooltipCoord = geom.getInteriorPoint().getCoordinates();//坐标
                      } else if (geom instanceof ol.geom.LineString) {
                          output = formatLength( /** @type {ol.geom.LineString} */(geom));//长度值
                          tooltipCoord = geom.getL