display lat lon in overlay maps

i have an overlay maps and this is the code (CODE:A)

var overlay;
  USGSOverlay.prototype = new google.maps.OverlayView();

  // Initialize the map and the custom overlay.

  function initMap() {
    var map = new google.maps.Map(document.getElementById('map'), {
      zoom: 5,
      center: {lat: -2.548926, lng: 118.0148634},
      mapTypeId: google.maps.MapTypeId.roadmap
    });

    var bounds = new google.maps.LatLngBounds(
        new google.maps.LatLng(-21.44555, -272.788888),
        new google.maps.LatLng(16.776667, -212.22222));

    var srcImage = 'http://localhost/komposat/no2.png';

    overlay = new USGSOverlay(bounds, srcImage, map);
  }

  function USGSOverlay(bounds, image, map) {

    // Initialize all properties.
    this.bounds_ = bounds;
    this.image_ = image;
    this.map_ = map;


    this.div_ = null;


    this.setMap(map);
  }

  USGSOverlay.prototype.onAdd = function() {

    var div = document.createElement('div');
    div.style.borderStyle = 'none';
    div.style.borderWidth = '0px';
    div.style.position = 'absolute';


    var img = document.createElement('img');
    img.src = this.image_;
    img.style.width = '100%';
    img.style.height = '100%';
    img.style.position = 'absolute';
    div.appendChild(img);

    this.div_ = div;
    this.div_.style.opacity = 0.5;


    var panes = this.getPanes();
    panes.overlayLayer.appendChild(div);
  };

    var sw = overlayProjection.fromLatLngToDivPixel(this.bounds_.getSouthWest());
    var ne = overlayProjection.fromLatLngToDivPixel(this.bounds_.getNorthEast());

    // Resize the image's div to fit the indicated dimensions.
    var div = this.div_;
    div.style.left = sw.x + 'px';
    div.style.top = ne.y + 'px';
    div.style.width = (ne.x - sw.x) + 'px';
    div.style.height = (sw.y - ne.y) + 'px';
  };

  USGSOverlay.prototype.onRemove = function() {
    this.div_.parentNode.removeChild(this.div_);
    this.div_ = null;
  };


  google.maps.event.addDomListener(window, 'load', initMap);

i want display lat and lng a location when the maps clicked by user. and this is the code (CODE:B)

google.maps.event.addListener(map, 'click', function( event )
            {
                  alert( "Latitude: "+event.latLng.lat()+" "+", longitude: "+event.latLng.lng() ); 

              });

i want to display lat and lng wherever user wants in my overlay map. i put my code:B inside the initMap function in code:A, but it didnt work. so can you guys help me solve this? thanks.