JS Geolocation Loop If Page Is Topmost SRC

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