How to use google maps API with multiple markers on the same map

Question

So, i have the following script to use the google maps API, its all fine, but i need to create a map that has more than one Marker (the balloon shaped icon pointing to something) and i need each of those markers to point on a different area of the map (i.e. different coordinates), how can i do it?

<script type="text/javascript">

         function load() {

        var map = new GMap2(document.getElementById("map"));
        var marker = new GMarker(new GLatLng(<%=coordinates%>));

        var html="<img src='simplemap_logo.jpg' width='20' height='20'/> " +
             "<%=maptitle%><br/>" +
             "<%=text%>";



        map.setCenter(new GLatLng(<%=coordinates%>), <%=zoom%>)
        map.setMapType(G_HYBRID_MAP);
        map.addOverlay(marker);
        map.addControl(new GLargeMapControl());
        map.addControl(new GScaleControl());
        map.addControl(new GMapTypeControl());


        marker.openInfoWindowHtml(html);
        }

        //]]>
        </script>

One more question, if i pass the Script text as a variable, lets say something like:

<script type="text/javascript">
<%=ScriptText%>
</script>

and my <%=ScriptText%> will be a string which i will build and assign its value to a Friend or Public variable called ScriptText, will it still run and work properly? (i am doing this to make my script dynamic and different based on how i build it as a STRING, due to my illiteracy in javascripting ;P)

Answer 1

obeattie and gregers are both right. In general, you need to store the marker parameters in some kind of array which you will later use at-least twice:

1. when adding the overlay to the map
2. when adding it to a GLatLngBounds object to calculate the center point and zoom level

The array or markers would look like an array of objects, something like:

var latlng1 = [
    new GLatLng( 48.1234, -120.1234 ),
    new GLatLng( 48.5678, -120.5678 ),
    new GLatLng( 48.9101, -120.9112 ),
    new GLatLng( 48.1121, -120.1314 ),
    new GLatLng( 48.3145, -120.1516 ),
    new GLatLng( 48.1617, -120.1718 ),
    new GLatLng( 48.1819, -120.1920 ),
    new GLatLng( 48.2021, -120.2122 )
];

The code for adding markers would look something similar to:

  // assume that map1 is an instance of a GMap2 object

  // #0 -- google maps api requires us to call setCenter first before calling any other operation on the map
  map1.setCenter( new GLatLng( 0, 0 ), 0 );

  // #1 -- add markers
  for ( var i = 0; i < latlng1.length; i++ )
  {
    var marker = new GMarker( latlng1[ i ] );
    map1.addOverlay( marker );
  }

  // #2a -- calculate center
  var latlngbounds = new GLatLngBounds( );
  for ( var i = 0; i < latlng1.length; i++ )
  {
    latlngbounds.extend( latlng1[ i ] );
  }

  // #2b -- set center using the calculated values
  map1.setCenter( latlngbounds.getCenter( ), map1.getBoundsZoomLevel( latlngbounds ) );

As for your question about using server side script inside client side javascript, yes you can mix them together. Judging by your description, i think this is what you need to do:

<script type="text/javascript">
    var latlng1 = new Array( );
</script>
<script type="text/javascript">
    <%
        do until rs.eof
            %>
            latlng1.push( new GLatLng( parseFloat( '<%= rs( "Lat" ) %>' ), parseFloat( '<%= rs( "Lng" ) %>' ) ) );
            <%
            rs.movenext
        loop
    %>
</script>

I've posted an article at: http://salman-w.blogspot.com/2009/03/zoom-to-fit-all-markers-polylines-or.html