请帮忙看看这段javascript代码问题出在哪里？

<SCRIPT language=javascript>
function next()
{
  document.formType.action = "throwinfo.htm";
  var chks = document.formType.infoType
  for(var i=0;i<chks.length;i++)
  {
    if (chks[i].checked && chks[i].value == "3")
    {
      document.formType.action = "throwinfo_zp.htm";
    }
  }
}
</SCRIPT>