DOM.addEventListener(window, 'load', function () {
  var form   = document.getElementById('bookingStarter'),
      side   = document.getElementById('starterSide'),
      street = document.getElementById('starterStreet');
  DOM.addEventListener(form, 'submit', function () {
    var prefix = side.options[side.selectedIndex].value;
    form.elements[prefix+'Type'].value   = 'LOCATION';
    form.elements[prefix+'Street'].value = street.value;
  });
});