Setting layer visibility – map.layers[0].visible not working

[wahlatlas]

I was wondering what the correct way of switching layer visibility was.
Currently for switching hillshading on/off I use

   function showHillShade(show) {

      if (show) {

         map.layers = [hillShade, backgroundLayer, dataLayer]

      } else {

         map.layers = [backgroundLayer, dataLayer]

      }

      map.redraw()

   }

see testcase 153
https://wahlatlas.net/experimente/testcases/gridviz3_issue_153_mapLayersVisible.html

but I was wondering if map.layers[0].visible=true could be used for this as well