add google maps to website with marker

<script src="https://maps.googleapis.com/maps/api/js"></script>
<script>
  function initialize() {
  	var myLatLng = {lat: 18.38162, lng: -66.133667};
    var mapCanvas = document.getElementById('map');
    var mapOptions = {
      center: myLatLng,
      zoom: 18,
      mapTypeId: google.maps.MapTypeId.ROADMAP
    }
    var marker = new google.maps.Marker({
	    position: myLatLng,
	    map: map,
	    title: 'Hello World!'
	  });
    var map = new google.maps.Map(mapCanvas, mapOptions);
	  marker.setMap(map);
  }
  google.maps.event.addDomListener(window, 'load', initialize);
</script>