Question

According to the documention a marker is optional with an infoWindow, so how is this achieved please? I have tried infowindow.open(map) and infowindow.open(map,null) but both produce nothing.

Answer 1

infowindow.open(map) makes no sense since you need to specify the position where the infowindow should open, also it has a tapered stem which specifies the location where it should point.

According to the documentation of Infowindows- InfoWindows may be attached to either Marker objects (in which case their position is based on the marker’s location) or on the map itself at a specified LatLng.

So if you donot want the marker to open the infowindow, use the map click event-

var iwindow= new google.maps.InfoWindow;
    google.maps.event.addListener(map,'click',function(event)
    {
         iwindow.setContent(event.latLng.lat()+","+event.latLng.lng());
         iwindow.open(map,this); 
         iwindow.open(map,this);
    });

And to close a InfowWindow- infowindow.setMap(null);

Hope that cleared your doubts.