Google Maps Clusterer

Question

如何让这件事有用？

我的代码是：

<script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=false"></script> 
<script type="text/javascript">
    var markers = [];
    var markerClusterer = null;
    var map = null;

    function initialize()
    {
        var center = new google.maps.LatLng(65, 45);
        var options = {
            'zoom': 4,
            'center': center,
            'mapTypeId': google.maps.MapTypeId.ROADMAP
        };

        map = new google.maps.Map(document.getElementById("map"), options);
        markerClusterer = new MarkerClusterer(map);
        alert(1);
    }
    $(document).ready(function() { initialize(); });
</script>

我甚至无法获得alert(1);？

我做错了什么？