Empty text box

hi,just wanna ask
i created textboxes to display data from an xml file but for those unused textboxes,the word “undefined” appears on them
eg i created 6 textboxes but i only have 2 data to display.the other 4 textboxes displays the word “undefined”
how to i make the textboxes empty?as in i dont want the word undefined to be on it
_root.NoPlate = this.firstChild.childNodes[0].childNodes[0].firstChild.nodeValue;
_root.TimeIn = this.firstChild.childNodes[0].childNodes[1].firstChild.nodeValue;
plate1.text = _root.NoPlate;
time1.text = _root.TimeIn;
hi,the code above is the declaration for my textbox
as u can see there isnt any declaration like plate1.text = “unassigned”
how do i assign an empty string to it?
do i write it like plate1.text = “” or plate1.text = NULL or something like that?