(function() {
  var mX, mY, distance,
    $distance = $('#distance span'),
    $element = $('#element');
  function calculateDistance(elem, mouseX, mouseY) {
    return Math.floor(Math.sqrt(Math.pow(mouseX - (elem.offset().left+(elem.width()/2)), 2) + Math.pow(mouseY - (elem.offset().top+(elem.height()/2)), 2)));
  }
  $(document).mousemove(function(e) { 
    mX = e.pageX;
    mY = e.pageY;
    distance = calculateDistance($element, mX, mY);
    $distance.text(distance);     
  });
})();