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Asked: 2026-05-23T12:32:20+00:00

I’m working on a project using Google Maps v3 that will allow users to

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I’m working on a project using Google Maps v3 that will allow users to drag and drop randomly placed markers (quantity, coordinates, and labels generated with php).

I would like the latitude and longitude of moved markers to update html input fields on the page.
Unfortunately, I do not know enough about js to give each marker a unique identity in an efficient way by using arrays and/or ‘variable variables’.

Here is my code thus far:

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
<style type="text/css">
  html { height: 100% }
  body { height: 100%; margin: 0px; padding: 0px }
  #map_canvas { height: 100% }
</style>
<script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=true"></script>
<script type="text/javascript">
function initialize() 
{
    var latlng = new google.maps.LatLng(39.3939,-119.861);
    var myOptions = 
    {
      zoom: 17,
      center: latlng,
      mapTypeId: google.maps.MapTypeId.SATELLITE
    };
    var map = new google.maps.Map(document.getElementById("map_canvas"),
        myOptions);

    // Set Border Coords
    var BorderCoords = 
    [
        new google.maps.LatLng(39.3952726888,-119.85922848),
        new google.maps.LatLng(39.3925273112,-119.85922848),
        new google.maps.LatLng(39.3925273112,-119.86277152),
        new google.maps.LatLng(39.3952726888,-119.86277152)   
    ];      

    // Define Border
    Border = new google.maps.Polygon
    ({
        map: map,
        paths: BorderCoords,
        strokeColor: "#FF0000",
        strokeOpacity: 0.8,
        strokeWeight: 2
    });

    // Set marker coords
    var MarkerCoords =
    [
        [39.3930761,-119.8612324],
        [39.3947606,-119.8617452],
        [39.3948516,-119.8619689],
        [39.3929412,-119.859542],
        [39.3947902,-119.8601571],
        [39.3940501,-119.8593369]
    ];

    // Set marker properties
    var MarkerProp = 
    [
        ["Red","A"],
        ["Red","B"],
        ["Red","C"],
        ["Blue","A"],
        ["Blue","B"],
        ["Blue","C"]
    ];

    // Define marker coords
    for (var i = 0; i < MarkerCoords.length; i++)
    {
        var markers = new google.maps.Marker
        ({
            map: map,
            position: new google.maps.LatLng(MarkerCoords[i][0],MarkerCoords[i][1]),
            clickable: true,
            draggable: true,
            icon: 'img/icons/'+MarkerProp[i][0]+'/letter_'+MarkerProp[i][1]+'.png'
        });

        google.maps.event.addListener(markers, "dragend", function() 
        {
            //These variables will not work
            //var latstr = eval('lat_'+MarkerProp[i][0]+'_'+MarkerProp[i][1]);
            //var lngstr = eval('lng_'+MarkerProp[i][0]+'_'+MarkerProp[i][1]);
            //var lat = document.getElementById(latstr);
            //var lng = document.getElementById(lngstr);

            //these lat/lng variables work for only one set of input fields
            var lat = document.getElementById('lat_Blue_C');
            var lng = document.getElementById('lng_Blue_C');
            var coords = this.getPosition()
            lat.value = coords.lat();
            lng.value = coords.lng();
        });
    }
}
</script>

</head>
<body onload="initialize()">
<div id="map_canvas" style="width:700px; height:400px"></div>
<br/>
<input id="lat_Red_A" type="text">
<input id="lng_Red_A" type="text">
<br/>
<input id="lat_Red_B" type="text">
<input id="lng_Red_B" type="text">
<br/>
<input id="lat_Red_C" type="text">
<input id="lng_Red_C" type="text">
<br/>
<input id="lat_Blue_A" type="text">
<input id="lng_Blue_A" type="text">
<br/>
<input id="lat_Blue_B" type="text">
<input id="lng_Blue_B" type="text">
<br/>
<input id="lat_Blue_C" type="text">
<input id="lng_Blue_C" type="text">
<br/>
</body>

</html>
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1 Answer

  1. Editorial Team

    Here is the answer. Define a custom id based on your marker properties and based on that access yout input field ids:

    <!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
<style type="text/css">
  html { height: 100% }
  body { height: 100%; margin: 0px; padding: 0px }
  #map_canvas { height: 100% }
</style>
<script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=true"></script>
<script type="text/javascript">
function initialize() 
{
    var latlng = new google.maps.LatLng(39.3939,-119.861);
    var myOptions = 
    {
      zoom: 17,
      center: latlng,
      mapTypeId: google.maps.MapTypeId.SATELLITE
    };
    var map = new google.maps.Map(document.getElementById("map_canvas"),
        myOptions);

    // Set Border Coords
    var BorderCoords = 
    [
        new google.maps.LatLng(39.3952726888,-119.85922848),
        new google.maps.LatLng(39.3925273112,-119.85922848),
        new google.maps.LatLng(39.3925273112,-119.86277152),
        new google.maps.LatLng(39.3952726888,-119.86277152)   
    ];      

    // Define Border
    Border = new google.maps.Polygon
    ({
        map: map,
        paths: BorderCoords,
        strokeColor: "#FF0000",
        strokeOpacity: 0.8,
        strokeWeight: 2
    });

    // Set marker coords
    var MarkerCoords =
    [
        [39.3930761,-119.8612324],
        [39.3947606,-119.8617452],
        [39.3948516,-119.8619689],
        [39.3929412,-119.859542],
        [39.3947902,-119.8601571],
        [39.3940501,-119.8593369]
    ];

    // Set marker properties
    var MarkerProp = 
    [
        ["Red","A",],
        ["Red","B"],
        ["Red","C"],
        ["Blue","A"],
        ["Blue","B"],
        ["Blue","C"]
    ];

    // Define marker coords
    for (var i = 0; i < MarkerCoords.length; i++)
    {
        var markers = new google.maps.Marker
        ({
            map: map,
            position: new google.maps.LatLng(MarkerCoords[i][0],MarkerCoords[i][1]),
            clickable: true,
            draggable: true,

            //define a custom id based on marker properties

            my_id: MarkerProp[i][0] +"_"+MarkerProp[i][1],
            icon: 'img/icons/'+MarkerProp[i][0]+'/letter_'+MarkerProp[i][1]+'.png'
        });

        google.maps.event.addListener(markers, "dragend", function() 
        {
            //These variables will not work
            //var latstr = eval('lat_'+MarkerProp[i][0]+'_'+MarkerProp[i][1]);
            //var lngstr = eval('lng_'+MarkerProp[i][0]+'_'+MarkerProp[i][1]);
            //var lat = document.getElementById(latstr);
            //var lng = document.getElementById(lngstr);

//get the id of the marker
var marker_id = this.my_id;



            //match the fields to update
            var lat = document.getElementById('lat_' + marker_id);
            var lng = document.getElementById('lng_' + marker_id);
            var coords = this.getPosition()
            lat.value = coords.lat();
            lng.value = coords.lng();
        });
    }
}
</script>

</head>
<body onload="initialize()">
<div id="map_canvas" style="width:700px; height:400px"></div>
<br/>
<input id="lat_Red_A" type="text">
<input id="lng_Red_A" type="text">
<br/>
<input id="lat_Red_B" type="text">
<input id="lng_Red_B" type="text">
<br/>
<input id="lat_Red_C" type="text">
<input id="lng_Red_C" type="text">
<br/>
<input id="lat_Blue_A" type="text">
<input id="lng_Blue_A" type="text">
<br/>
<input id="lat_Blue_B" type="text">
<input id="lng_Blue_B" type="text">
<br/>
<input id="lat_Blue_C" type="text">
<input id="lng_Blue_C" type="text">
<br/>
</body>

</html>
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