大家帮忙来看看程序出了什么问题

a.js的内容
function isInvalidDate(theDate,separator){
  default_style=1
  if (theDate.length>10 || theDate.length<8)
    return true
  idx1=theDate.indexOf(separator)
  if (idx1==-1)
    return true
  idx2=theDate.indexOf(separator,idx1+1)
  if (idx2==-1)
    return true
  if (isInvalidDate.arguments.length>2)
   default_style=isInvalidDate.arguments[2]
  if (default_style<1 || default_style>9){
   alert("传入参数有误！请检查。")
return true
  }
  if (default_style==1){
  theYear=theDate.substring(0,idx1)
  theMonth=theDate.substring(idx1+1,idx2)
  theDay=theDate.substring(idx2+1)
  }
  if (default_style==2){
  theMonth=theDate.substring(0,idx1)
  theDay=theDate.substring(idx1+1,idx2)
  theYear=theDate.substring(idx2+1)
  }
  if (theDay.length>2)
    return true
  if (parseYMD(theYear,theMonth,theDay)>0)
    return true
  else
    return false
}