<select> problem

[Poornima]

Hello
I have a html page in which i have 2 list boxes.If i select an item
from listbox1 and click Add button it should get populated in the
listbox2.When i click ok all the items present in listbox2 should get
selected.But my problem is where there are no items in listbox2 are
also getting selected.

In short how to find out if an <option>is empty or not
I tried by writing the f'ing code

for(i=0;i<length1;i++) // length1 is the length of the listbox
{
if(x.options != null)
x.options.selected = true
else if(x.options == null)
x.options.selected = false
}

Thanks In Advance