Check Textboxes With No Value And Listbox

I am trying to check some textboxes if they have no value, and a listbox. However, with my current code, it seems like the OR code is not working like it should be.
<script type="text/javascript">
function checkEmpty() {
if (document.editForm.varenummer.value!="" || document.editForm.serienummer.value!="") {
if (document.all("reakke").options[document.all("reakke").selectedIndex].value == "2") {
alert();
} else {
document.editForm.submit();
}} else {
alert("Indtast venligst alle informationer");
}}
</script>
As seen above, if Varenummer or Serienummer is not equals nothing, then check the listbox, but if they are nothing then do the else statement. However as I tested, the else statement only triggers if both Varenummer and Serienummer is nothing.