如何添加谷歌地图标记

我将此地图添加到了我的网站，该地图可以正常工作，但是我无法显示该标记。

我尝试添加代码：

var marker = new google.maps.Marker({
              position: myLatLng,
              map: map,
              title: 'My Marker'
             });

但什么都没有出现。这是我的整个代码：

        var map;
        var myLatLng = new google.maps.LatLng(36.7394266,-119.792913);

      var marker = new google.maps.Marker({
              position: myLatLng,
              map: map,
              title: 'My Marker'
             });

        function initialize() {

            var roadAtlasStyles = [
  {
      "featureType": "road.highway",
      "elementType": "geometry",
      "stylers": [
        { "saturation": -100 },
        { "lightness": -8 },
        { "gamma": 1.18 }
      ]
  }, {
      "featureType": "road.arterial",
      "elementType": "geometry",
      "stylers": [
        { "saturation": -100 },
        { "gamma": 1 },
        { "lightness": -24 }
      ]
  }, {
      "featureType": "poi",
      "elementType": "geometry",
      "stylers": [
        { "saturation": -100 }
      ]
  }, {
      "featureType": "administrative",
      "stylers": [
        { "saturation": -100 }
      ]
  }, {
      "featureType": "transit",
      "stylers": [
        { "saturation": -100 }
      ]
  }, {
      "featureType": "water",
      "elementType": "geometry.fill",
      "stylers": [
        { "saturation": -100 }
      ]
  }, {
      "featureType": "road",
      "stylers": [
        { "saturation": -100 }
      ]
  }, {
      "featureType": "administrative",
      "stylers": [
        { "saturation": -100 }
      ]
  }, {
      "featureType": "landscape",
      "stylers": [
        { "saturation": -100 }
      ]
  }, {
      "featureType": "poi",
      "stylers": [
        { "saturation": -100 }
      ]
  }, {
  }
            ]

            var mapOptions = {
                zoom: 14,
                center: myLatLng,
                mapTypeControlOptions: {
                    mapTypeIds: [google.maps.MapTypeId.ROADMAP, 'usroadatlas']
                }
            };

            map = new google.maps.Map(document.getElementById('map-canvas'),
                mapOptions);

            var styledMapOptions = {

            };

            var usRoadMapType = new google.maps.StyledMapType(
                roadAtlasStyles, styledMapOptions);

            map.mapTypes.set('usroadatlas', usRoadMapType);
            map.setMapTypeId('usroadatlas');
        }

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