입력상자에서 자리수 차면 이동하기

<SCRIPT language=JavaScript>

function Nextchk(arg,len,nextname) {
if (arg.value.length==len) {
nextname.focus() ;
return;
}
}
</SCRIPT>


<FORM method=post name=zipcode>
우편번호<INPUT maxLength=3 name=zip1 size=3

     onkeyup='Nextchk(this,3,document.zipcode.zip2)'>
-
   <INPUT maxLength=3 name=zip2 size=3>
</FORM>