function cek_isian() {
  var nama=form_reservation.nama.value;
  var reEmail = /^.+\@.+\..+$/;
  var angka=/^[0-9]+$/;
  if (form_reservation.nama.value=='') {
		alert('fill your full name');
	    form_reservation.nama.focus();
	    return false;
  } 
  else if (nama.length < 4) {
     alert('must be at least 4 characters long');
	 form_reservation.nama.select();
	 return false;
  }
  else if (form_reservation.email.value=='') {
	  alert('check your e-mail address');
	  form_reservation.email.focus();
	  return false;
	  }
  else if( !reEmail.test( document.form_reservation.email.value ) ){
	  alert('not valid e-mail address');
	  form_reservation.email.select();
	  return false;
	}
   else if (form_reservation.phone.value=='') {
	  alert('check your phone number');
	  form_reservation.phone.focus();
	  return false;
	  }
   else if (form_reservation.address.value=='') {
	  alert('check your address');
	  form_reservation.address.focus();
	  return false;
	  }
    else if (form_reservation.tgl_arrival.value=='') {
      alert('select date arrival');
	  form_reservation.tgl_arrival.focus();
	  return false;
	  }
	else if (form_reservation.bulan_arrival.value=='') {
      alert('select month arrival');
	  form_reservation.bulan_arrival.focus();
	  return false;
	  }
	else if (form_reservation.tahun_arrival.value=='') {
      alert('select year arrival');
	  form_reservation.tahun_arrival.focus();
	  return false;
	  }
	else if (form_reservation.tgl_departure.value=='') {
      alert('select date departure');
	  form_reservation.tgl_departure.focus();
	  return false;
	  }
	else if (form_reservation.bulan_departure.value=='') {
      alert('select month departure');
	  form_reservation.bulan_departure.focus();
	  return false;
	  }
	else if (form_reservation.tahun_departure.value=='') {
      alert('select year departure');
	  form_reservation.tahun_departure.focus();
	  return false;
	  }
	else if (form_reservation.typeofroom.value=='') {
      alert('select room type');
	  form_reservation.typeofroom.focus();
	  return false;
	  }
	else if (form_reservation.person.value=='') {
      alert('check how many person?');
	  form_reservation.person.focus();
	  return false;
	  }
	else if( !angka.test( form_reservation.person.value ) ){
	  alert('only number can accepted');
	  form_reservation.person.select();
	  return false;
	  }
	else if (form_reservation.person.value<1) {
      alert('Minimum 1 person?');
	  form_reservation.person.select();
	  return false;
	  }
	  else {
	   var setuju=window.confirm('All information done?');
	    if (setuju) {
		  true;
		}
		else {
		  return setuju;
		 }
	  }
}