js擷取字元串長度

<SCRIPT LANGUAGE="JavaScript">
<!--
function Len(str)
{
     var i,sum;
     sum=0;
     for(i=0;i<str.length;i++)
     {
         if ((str.charCodeAt(i)>=0) && (str.charCodeAt(i)<=255))
             sum=sum+1;
         else
             sum=sum+2;
     }
     return sum;
}
function checkPasswordLen(){
   passwd1   = document.getElementById('passwd').value;
   if(Len(passwd1)<6)
   {
    alert("密碼長度不能小于6！");
    document.getElementById('passwd').focus();
   }

}

           

</SCRIPT >