cript&gt;
      // Transparent Proj4js support:
      //
      // EPSG:21781 is known to Proj4js because its definition was loaded in the html.
      // Now when we create an ol.proj.Projection instance with the &#x27;EPSG:21781&#x27; code,
      // OpenLayers will pick up parameters like units and transform functions from
      // Proj4js.
      //
      // Note that we are setting the projection&#x27;s extent here, which is used to
      // determine the view resolution for zoom level 0. Recommended value