JS Display Current Local Geo Location SRC

<!DOCTYPE html>
<html>
<center>
<button onclick="Loc();">Location</button>
<script>
function Loc()
{
var loc = document.getElementById("demo");
    if (navigator.geolocation) {
        navigator.geolocation.getCurrentPosition(showPosition);
    } else {
        alert("Geolocation is not supported by this browser.");
    }
}
function showPosition(position) {
alert("Latitude: " +position.coords.latitude+"\n\n"+"Longitude:" +
position.coords.longitude,"Your Current Location");
document.writeln("<center>Geo Location:<p>"+position.coords.latitude+'<p>');
document.writeln(position.coords.longitude+'<p>');
}
</script>
<center>
</html>