Until now, we only see how to do reprojection using points coordinates but how can we do it for extent?
ol.proj.transformExtent(extent, 'EPSG:21781', 'EPSG:4326');
We reused the function behind the
ol.proj.transform function without knowledge.
ol.proj.transformExtent method expects an extent as a first parameter, as a second parameter, it needs the origin projection, and as a third parameter, it's the destination ...