Microsoft's Active Server Pages (ASP) technology (or, Classic ASP as it's called these days) was designed to an easy way to build web applications: just code some HTML and sprinkle some VBScript between <'% ... %> blocks. It was (and, for the most part, still can be) a decent, simple tool for building simple things.

Of course, there's one big problem with simple tools: they're simple, and certain developers are too smart for simple. And that brings us to Catherine P, who's found herself maintaining a sprawling mess of a Classic ASP system that should have been retired years ago. Of the many "innovative and unique" patterns introduced by the original developer is "limiting the amount of JavaScript sent to the browser." As to how is this wizardy is accomplished... there is code like this is in the header of each page.

<head>
...
<script language="JavaScript"><!--

  // Get date checking functions
  <% = CheckDateFunction %>
  <% = IsNumericFunction %>

//-->
</script>
</head>

So long as you include client_functions.asp, you can simply "reference" whatever JavaScript functions are needed on the page, without needing to have the browser download all sorts of code it won't use for that page.

<% 
'''''''''''''''''''''''''''''''''''''''''''''''''''''
' client_functions.asp
'''''''''''''''''''''''''''''''''''''''''''''''''''''

Function CheckDateFunction()
' Returns the HTML/Javascript required to produce the CheckDate() function.
 Dim strHTML

 strHTML = strHTML & "function CheckDate(strDate, strCentury)" & vbCrLf
 strHTML = strHTML & "{" & vbCrLf
 strHTML = strHTML & "  var strToday = new Date(); " & vbCrLf
 strHTML = strHTML & "  var strDay = '';" & vbCrLf
 strHTML = strHTML & "  var strMonth = '';" & vbCrLf
 strHTML = strHTML & "  var strYear = '';" & vbCrLf
 strHTML = strHTML & "  var intPos; " & vbCrLf
 strHTML = strHTML & "  var strMonthname;" & vbCrLf
 strHTML = strHTML & "  var strFinalDate;" & vbCrLf
 strHTML = strHTML & "    var blnIsLeapYear" & vbCrLf
 strHTML = strHTML & "    var strLastValidDay" & vbCrLf
 strHTML = strHTML & "  strMonthName = new Array('Dummy', 'Jan', 'Feb', 'Mar', 'Apr', "
 strHTML = strHTML & "   'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec');" & vbCrLf
 strHTML = strHTML & "    intPos = 0" & vbCrLf
 strHTML = strHTML & "  while(IsNumeric(strDate.charAt(intPos)) && intPos < strDate.length){" & vbCrLf
 strHTML = strHTML & "    strDay += strDate.charAt(intPos);" & vbCrLf
 strHTML = strHTML & "    intPos++;" & vbCrLf
 strHTML = strHTML & "  }" & vbCrLf
 strHTML = strHTML & "  if(strDate.charAt(intPos) != ' ' && strDate.charAt(intPos) != '.' &&  "
 strHTML = strHTML & "     strDate.charAt(intPos) != '/' && strDate.charAt(intPos) != '-') " & vbCrLf
 strHTML = strHTML & "    return('');" & vbCrLf
 strHTML = strHTML & "  while((strDate.charAt(intPos) == ' ' || strDate.charAt(intPos) == '.' ||  "
 strHTML = strHTML & "         strDate.charAt(intPos) == '/' || strDate.charAt(intPos) == '-') &&  "
 strHTML = strHTML & "         intPos < strDate.length)" & vbCrLf
 strHTML = strHTML & "    intPos += 1;" & vbCrLf
 strHTML = strHTML & "  while(strDate.charAt(intPos) != ' ' && strDate.charAt(intPos) != '.' &&  "
 strHTML = strHTML & "        strDate.charAt(intPos) != '/' && strDate.charAt(intPos) != '-' &&  "
 strHTML = strHTML & "        intPos < strDate.length){" & vbCrLf
 strHTML = strHTML & "    strMonth += strDate.charAt(intPos);" & vbCrLf
 strHTML = strHTML & "    intPos += 1;" & vbCrLf
 strHTML = strHTML & "  }" & vbCrLf
 strHTML = strHTML & "  while((strDate.charAt(intPos) == ' ' || strDate.charAt(intPos) == '.' ||  "
 strHTML = strHTML & "         strDate.charAt(intPos) == '/' || strDate.charAt(intPos) == '-') &&  "
 strHTML = strHTML & "         intPos < strDate.length)" & vbCrLf
 strHTML = strHTML & "    intPos += 1;" & vbCrLf
 strHTML = strHTML & "  while(intPos < strDate.length){" & vbCrLf
 strHTML = strHTML & "    strYear += strDate.charAt(intPos);" & vbCrLf
 strHTML = strHTML & "    intPos += 1;" & vbCrLf
 strHTML = strHTML & "  }" & vbCrLf
 strHTML = strHTML & "  if(!strCentury){ " & vbCrLf
 strHTML = strHTML & "    if(strYear == ''){" & vbCrLf
 strHTML = strHTML & "      today = new Date()" & vbCrLf
 strHTML = strHTML & "      strYear = today.getFullYear();" & vbCrLf
 strHTML = strHTML & "        }" & vbCrLf
 strHTML = strHTML & "    else{" & vbCrLf
 strHTML = strHTML & "      if(strYear < 70){   " & vbCrLf
 strHTML = strHTML & "              if(parseInt(strYear,10) < 10)  " & vbCrLf
 strHTML = strHTML & "                    strYear = '0' + parseInt(strYear,10)" & vbCrLf
 strHTML = strHTML & "              strYear = '20' + strYear;" & vbCrLf
 strHTML = strHTML & "            }" & vbCrLf
 strHTML = strHTML & "      else{" & vbCrLf
 strHTML = strHTML & "        if(strYear < 100)" & vbCrLf
 strHTML = strHTML & "          strYear = '19' + strYear;" & vbCrLf
 strHTML = strHTML & "      }" & vbCrLf
 strHTML = strHTML & "    }" & vbCrLf
 strHTML = strHTML & "  }" & vbCrLf
 strHTML = strHTML & "  else{ " & vbCrLf
 strHTML = strHTML & "    if(strYear == ''){" & vbCrLf
 strHTML = strHTML & "      today = new Date()" & vbCrLf
 strHTML = strHTML & "      strYear = today.getFullYear();" & vbCrLf
 strHTML = strHTML & "        }" & vbCrLf
 strHTML = strHTML & "        else{" & vbCrLf
 strHTML = strHTML & "            if(parseInt(strYear, 10) < 100){" & vbCrLf
 strHTML = strHTML & "                if(parseInt(strYear, 10) < 10)" & vbCrLf
 strHTML = strHTML & "                    strYear = '0' + parseInt(strYear,10)" & vbCrLf
 strHTML = strHTML & "                strYear = strCentury + strYear;" & vbCrLf
 strHTML = strHTML & "            }" & vbCrLf
 strHTML = strHTML & "        }" & vbCrLf
 strHTML = strHTML & "  }" & vbCrLf
 strHTML = strHTML & "  if(!(IsNumeric(strDay) && IsNumeric(strYear)))" & vbCrLf
 strHTML = strHTML & "    return ('') ;" & vbCrLf
 strHTML = strHTML & "  if(parseInt(strDay, 10) < 10)" & vbCrLf
 strHTML = strHTML & "    strDay = '0' + parseInt(strDay,10)" & vbCrLf
 strHTML = strHTML & "  if(IsNumeric(strMonth) && parseInt(strMonth, 10) > 0 &&  "
 strHTML = strHTML & "     parseInt(strMonth,10) < 13)" & vbCrLf
 strHTML = strHTML & "    strMonth = strMonthName[parseInt(strMonth, 10)];" & vbCrLf
 strHTML = strHTML & "  if(parseInt(strYear, 10) < 0 || parseInt(strYear,10) > 9999)" & vbCrLf
 strHTML = strHTML & "    return '' " & vbCrLf
 strHTML = strHTML & "    if(parseInt(strYear, 10) % 400 == 0)" & vbCrLf
 strHTML = strHTML & "        blnIsLeapYear = true;" & vbCrLf
 strHTML = strHTML & "    else{" & vbCrLf
 strHTML = strHTML & "        if(parseInt(strYear, 10) % 100 == 0)" & vbCrLf
 strHTML = strHTML & "            blnIsLeapYear = false;" & vbCrLf
 strHTML = strHTML & "        else{" & vbCrLf
 strHTML = strHTML & "            if(parseInt(strYear, 10) % 4 == 0)" & vbCrLf
 strHTML = strHTML & "                blnIsLeapYear = true;" & vbCrLf
 strHTML = strHTML & "            else" & vbCrLf
 strHTML = strHTML & "                blnIsLeapYear = false;" & vbCrLf
 strHTML = strHTML & "        }" & vbCrLf
 strHTML = strHTML & "    }" & vbCrLf
 strHTML = strHTML & "    strMonth = strMonth.substr(0, 3)" & vbCrLf
 strHTML = strHTML & "    strMonth = strMonth.toLowerCase()" & vbCrLf
 strHTML = strHTML & "    switch(strMonth) {" & vbCrLf
 strHTML = strHTML & "    case 'jan' :" & vbCrLf
 strHTML = strHTML & "        strMonth = strMonthName[1];" & vbCrLf
 strHTML = strHTML & "        strLastValidDay = '31'" & vbCrLf
 strHTML = strHTML & "        break;" & vbCrLf
 strHTML = strHTML & "    case 'feb' :" & vbCrLf
 strHTML = strHTML & "        strMonth = strMonthName[2];" & vbCrLf
 strHTML = strHTML & "        blnIsLeapYear ? strLastValidDay = '29'  "
 strHTML = strHTML & "                      : strLastValidDay = '28'" & vbCrLf
 strHTML = strHTML & "        break;" & vbCrLf
 strHTML = strHTML & "    case 'mar' :" & vbCrLf
 strHTML = strHTML & "        strMonth = strMonthName[3];" & vbCrLf
 strHTML = strHTML & "        strLastValidDay = '31'" & vbCrLf
 strHTML = strHTML & "        break;" & vbCrLf
 strHTML = strHTML & "    case 'apr' :" & vbCrLf
 strHTML = strHTML & "        strMonth = strMonthName[4];" & vbCrLf
 strHTML = strHTML & "        strLastValidDay = '30'" & vbCrLf
 strHTML = strHTML & "        break;" & vbCrLf
 strHTML = strHTML & "    case 'may' :" & vbCrLf
 strHTML = strHTML & "        strMonth = strMonthName[5];" & vbCrLf
 strHTML = strHTML & "        strLastValidDay = '31'" & vbCrLf
 strHTML = strHTML & "        break;" & vbCrLf
 strHTML = strHTML & "    case 'jun' :" & vbCrLf
 strHTML = strHTML & "        strMonth = strMonthName[6];" & vbCrLf
 strHTML = strHTML & "        strLastValidDay = '30'" & vbCrLf
 strHTML = strHTML & "        break;" & vbCrLf
 strHTML = strHTML & "    case 'jul' :" & vbCrLf
 strHTML = strHTML & "        strMonth = strMonthName[7];" & vbCrLf
 strHTML = strHTML & "        strLastValidDay = '31'" & vbCrLf
 strHTML = strHTML & "        break;" & vbCrLf
 strHTML = strHTML & "    case 'aug' :" & vbCrLf
 strHTML = strHTML & "        strMonth = strMonthName[8];" & vbCrLf
 strHTML = strHTML & "        strLastValidDay = '31'" & vbCrLf
 strHTML = strHTML & "        break;" & vbCrLf
 strHTML = strHTML & "    case 'sep' :" & vbCrLf
 strHTML = strHTML & "        strMonth = strMonthName[9];" & vbCrLf
 strHTML = strHTML & "        strLastValidDay = '30'" & vbCrLf
 strHTML = strHTML & "    break;" & vbCrLf
 strHTML = strHTML & "    case 'oct' :" & vbCrLf
 strHTML = strHTML & "        strMonth = strMonthName[10];" & vbCrLf
 strHTML = strHTML & "        strLastValidDay = '31'" & vbCrLf
 strHTML = strHTML & "        break;" & vbCrLf
 strHTML = strHTML & "    case 'nov' :" & vbCrLf
 strHTML = strHTML & "        strMonth = strMonthName[11];" & vbCrLf
 strHTML = strHTML & "        strLastValidDay = '30'" & vbCrLf
 strHTML = strHTML & "        break;" & vbCrLf
 strHTML = strHTML & "    case 'dec' :" & vbCrLf
 strHTML = strHTML & "        strMonth = strMonthName[12];" & vbCrLf
 strHTML = strHTML & "        strLastValidDay = '31'" & vbCrLf
 strHTML = strHTML & "        break;" & vbCrLf
 strHTML = strHTML & "    default : " & vbCrLf
 strHTML = strHTML & "        return ''" & vbCrLf
 strHTML = strHTML & "    }" & vbCrLf
 strHTML = strHTML & "    if(parseInt(strDay,10) < 1 || parseInt(strDay, 10) >  "
 strHTML = strHTML & "           parseInt(strLastValidDay, 10))" & vbCrLf
 strHTML = strHTML & "        return '';" & vbCrLf
 strHTML = strHTML & "  strFinalDate = strDay + ' ' + strMonth + ' ' + strYear;" & vbCrLf
 strHTML = strHTML & "  return strFinalDate" & vbCrLf
 strHTML = strHTML & "}" & vbCrLf & vbCrLf
 CheckDateFunction = strHTML
End Function

Public Function IsNumericFunction()
' Returns the HTML/Javascript required to produce the IsNumeric() function.
 Dim strHTML
 strHTML = strHTML & "function IsNumeric(strNum)" & vbCrLf
 strHTML = strHTML & "{" & vbCrLf
 strHTML = strHTML & "    var intCount = 0;" & vbCrLf
 strHTML = strHTML & "    blnIsNumeric = new Boolean(true);    " & vbCrLf
 strHTML = strHTML & "    while(intCount < strNum.length){" & vbCrLf
 strHTML = strHTML & "        if(!(parseInt(strNum.charAt(intCount), 10) >=0 &&  "
 strHTML = strHTML & "             parseInt(strNum.charAt(intCount), 10) <= 9))" & vbCrLf
 strHTML = strHTML & "            blnIsNumeric = false;" & vbCrLf
 strHTML = strHTML & "        intCount++;" & vbCrLf
 strHTML = strHTML & "    }" & vbCrLf
 strHTML = strHTML & "    return(blnIsNumeric);" & vbCrLf
 strHTML = strHTML & "}" & vbCrLf & vbCrLf
 IsNumericFunction = strHTML
End Function

... snip many, many more ...
%>