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I am writing JavaScript code using Google Maps API.
map = new google.maps.Map2(document.getElementById("map_canvas"));
map.setCenter(new google.maps.LatLng(37.4419, -122.1419), 13);
The above code sets the default location of the map canvas to Palo Alto.
How can we write the script in such a way that the setCenter function automatically points to the current location of the client?
513
You can use the HTML5 GeoLocation API in browsers that support it.
if (navigator.geolocation) {
navigator.geolocation.getCurrentPosition(success, error);
} else {
alert('geolocation not supported');
}
function success(position) {
alert(position.coords.latitude + ', ' + position.coords.longitude);
}
function error(msg) {
alert('error: ' + msg);
}
I can think of two possible options.
First you may want to consider using the GeoLocation API as ceejayoz suggested. This is very easy to implement, and it is a fully client-side solution. To center the map using GeoLocation, simply use:
map.setCenter(new google.maps.LatLng(position.coords.latitude,
position.coords.longitude), 13);
... inside the success() callback of the GeoLocation's getCurrentPosition() method.
Unfortunately only a few modern browsers are currently supporting the GeoLocation API. Therefore you can also consider using a server-side solution to resolve the IP address of the client into the user's location, using a service such as MaxMind's GeoLite City. Then you can simply geocode the city and country of the user inside the browser, using the Google Maps API. The following could be a brief example:
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8"/>
<title>Google Maps API Geocoding Demo</title>
<script src="http://maps.google.com/maps?file=api&v=2&sensor=false"
type="text/javascript"></script>
</head>
<body onunload="GUnload()">
<div id="map_canvas" style="width: 400px; height: 300px"></div>
<script type="text/javascript">
var userLocation = 'London, UK';
if (GBrowserIsCompatible()) {
var geocoder = new GClientGeocoder();
geocoder.getLocations(userLocation, function (locations) {
if (locations.Placemark) {
var north = locations.Placemark[0].ExtendedData.LatLonBox.north;
var south = locations.Placemark[0].ExtendedData.LatLonBox.south;
var east = locations.Placemark[0].ExtendedData.LatLonBox.east;
var west = locations.Placemark[0].ExtendedData.LatLonBox.west;
var bounds = new GLatLngBounds(new GLatLng(south, west),
new GLatLng(north, east));
var map = new GMap2(document.getElementById("map_canvas"));
map.setCenter(bounds.getCenter(), map.getBoundsZoomLevel(bounds));
map.addOverlay(new GMarker(bounds.getCenter()));
}
});
}
</script>
</body>
</html>
Simply replace userLocation = 'London, UK' with the server-side resolved address. The following is a screenshot from the above example:
You can remove the marker by getting rid of the map.addOverlay(new GMarker(bounds.getCenter())); line.
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