Edit in JSFiddle

var viewer = null

function initMap() {
  viewer = iv.getViewer();
  viewer.getMap().addControl(new Geoportal.Control.LayerSwitcher());
}

iv = Geoportal.load(
  'viewerDiv', 
  ['jhyvi0fgmnuxvfv0zjzorvdn'], 
  { // Positionnement par coordonnées
    lon : 2.294, 
    lat : 48.858
  },
  17, 
  {
    onView: initMap,
    layers: [
    'ORTHOIMAGERY.ORTHOPHOTOS',
    'GEOGRAPHICALGRIDSYSTEMS.MAPS'
    ]
  }
);



/*
window.onload=function(){
	
};
*/
#viewerDiv {
  width: 100%;
  height: 400px;
}

#info {
  padding: 5px;
  width: 100%;
  height: 20px;
  font-family: "monospace";
  font-size: 10px;
}
<div id="viewerDiv"></div>
<div id="info"></div>

External resources loaded into this fiddle: