Edit in JSFiddle

var xhr = new XMLHttpRequest();
xhr.open('GET', 'http://get-current-position.appspot.com', true);
xhr.onload = function() {
  var responseText = xhr.responseText;
  var coords = JSON.parse(responseText).coords; 
  var image = new Image();
  image.src = 'http://maps.googleapis.com/maps/api/staticmap?center=' + coords.latitude + ',' + coords.longitude + '&size=256x256&sensor=false&zoom=12';
  document.body.appendChild(image);
};
xhr.send();