I use to ajax to load my places from external json like this:
[{
  "id":"1",
  "title": "Stockholm",
  "lat": 59.3,
  "lng": 18.1,
},
{
  "id":"2",
  "title": "Oslo",
  "lat": 59.9,
  "lng": 10.8,
},
{
  "id":"2",
  "title": "Copenhagen",
  "lat": 55.7,
  "lng": 12.6,
}]
and my map load in page with a code like this:
var MapInitialized = false,
        $map           = $('#googleMap .map');
    var mapProp = {
        center:new google.maps.LatLng(35.6891970, 51.3889740),
        zoom:12,
        disableDefaultUI: true,
        zoomControl: true,
        mapTypeId: google.maps.MapTypeId.ROADMAP,
        scrollwheel: false,
        animation: google.maps.Animation.DROP,
        mapTypeControlOptions: {
            mapTypeIds: [google.maps.MapTypeId.ROADMAP, 'bestfromgoogle']
            }
        };
    var map = new google.maps.Map($map[0], mapProp);
    var infoWindow = new google.maps.InfoWindow();
    $("select").change(function(){
        $.ajax({
            type: "GET",
            url: "places.json",
            dataType: "json",
            beforeSend: function(){ $(".mapLoading").fadeIn();},
            complete: function(){ $(".mapLoading").fadeOut();},
            success: function(response){
                var LatLngList = new Array();
                var marker;
                $.each(response, function(key, data) {
                    Point = new google.maps.LatLng(data.lat, data.lng); 
                    LatLngList.push(Point);
                    console.log(LatLngList);
                     marker = new google.maps.Marker({
                        position: Point,
                        map: map,
                        title: data.title
                    });
                });
                var bounds = new google.maps.LatLngBounds ();
                for (var i = 0, LtLgLen = LatLngList.length; i < LtLgLen; i++) {
                    bounds.extend (LatLngList[i]);
                }
                map.fitBounds (bounds);
            }
        });
    });
I have a selector on my HTML page that when user change it ajax send request to json and marker will show on map. now i need to remove all previous marker and load new marker on map without loading a new map.