function $ (id) {
  return typeof id == 'string' ? document.getElementById(id) : id;
}

function listener (obj, type, callback) {
  obj.addEventListener
    ? obj.addEventListener(type, callback, false)
    : obj.attachEvent('on'+type, callback);
}

listener($('swapimage'), 'mouseover', function () {
  $('studentimage').setAttribute(
    'src', 'http://nipotan.org/female-student.jpg'
  );
});

listener($('swapimage'), 'mouseout', function () {
  $('studentimage').setAttribute(
    'src', 'http://nipotan.org/nipotan-student.jpg'
  );
});