I'm attempting to use Ajax to upload a file to a server-side script in classic ASP.

Here is the relevant HTML and JavaScript code:

<input type="file" id="fileInput" />

and

function saveToServer(file) {
    const fd = new FormData();
    fd.append('image', file);
    const xhr = new XMLHttpRequest();
    xhr.open('POST', 'http://localhost/post.asp', true);
    xhr.onload = () => {
        if (xhr.status === 200) {
            // Do stuff with response
        }
    };
    xhr.send(fd);
}

const fileInput = document.getElementById("fileInput");

fileInput.addEventListener("change", () => {
    const file = fileInput.files[0];
    if (/^image\//.test(file.type)) {
        saveToServer(file);
    } else {
        console.warn('You can only upload images.');
    }
});

My concern is: how do I access the uploaded file on my Classic ASP page (post.asp)?

In PHP, there's a global variable called $_FILES that would contain something like:

Array
(
  [image] => Array
  (
    [name] => cat.png
    [type] => image/png
    [tmp_name] => /tmp/phpOjXMW3
    [error] => 0
    [size] => 10603
  )
)

Is there an equivalent in Classic ASP?

---

This is the post page:

Set upl = New FileUploader 
upl.Upload()
If upl.Files.Count = 1 Then
  For Each File In upl.Files.Items
    If File.FileSize < 100000 Then
      File.FileName =  upl.Form ("id") & ".jpg"
      File.SaveToDisk Server.MapPath("/Images")
  next
end if

This is an include at the top of the post page:

Class FileUploader
    Public  Files
    Private mcolFormElem

    Private Sub Class_Initialize()
        Set Files = Server.CreateObject("Scripting.Dictionary")
        Set mcolFormElem = Server.CreateObject("Scripting.Dictionary")
    End Sub

    Private Sub Class_Terminate()
        If IsObject(Files) Then
            Files.RemoveAll()
            Set Files = Nothing
        End If
        If IsObject(mcolFormElem) Then
            mcolFormElem.RemoveAll()
            Set mcolFormElem = Nothing
        End If
    End Sub

    Public Property Get Form(sIndex)
        Form = ""
        If mcolFormElem.Exists(LCase(sIndex)) Then Form = mcolFormElem.Item(LCase(sIndex))
    End Property

    Public Default Sub Upload()
        Dim biData, sInputName
        Dim nPosBegin, nPosEnd, nPos, vDataBounds, nDataBoundPos
        Dim nPosFile, nPosBound
    'response.Flush

        biData = Request.BinaryRead(Request.TotalBytes)
        nPosBegin = 1
        nPosEnd = InstrB(nPosBegin, biData, CByteString(Chr(13)))

        If (nPosEnd-nPosBegin) <= 0 Then Exit Sub

        vDataBounds = MidB(biData, nPosBegin, nPosEnd-nPosBegin)
        nDataBoundPos = InstrB(1, biData, vDataBounds)

        Do Until nDataBoundPos = InstrB(biData, vDataBounds & CByteString("--"))

            nPos = InstrB(nDataBoundPos, biData, CByteString("Content-Disposition"))
            nPos = InstrB(nPos, biData, CByteString("name="))
            nPosBegin = nPos + 6
            nPosEnd = InstrB(nPosBegin, biData, CByteString(Chr(34)))
            sInputName = CWideString(MidB(biData, nPosBegin, nPosEnd-nPosBegin))
            nPosFile = InstrB(nDataBoundPos, biData, CByteString("filename="))
            nPosBound = InstrB(nPosEnd, biData, vDataBounds)

            If nPosFile <> 0 And  nPosFile < nPosBound Then
                Dim oUploadFile, sFileName
                Set oUploadFile = New UploadedFile

                oUploadFile.FormElement = MidB(biData, nPos, 5)


                nPosBegin = nPosFile + 10
                nPosEnd =  InstrB(nPosBegin, biData, CByteString(Chr(34)))
                sFileName = CWideString(MidB(biData, nPosBegin, nPosEnd-nPosBegin))
                oUploadFile.FileName = Right(sFileName, Len(sFileName)-InStrRev(sFileName, "\"))

                nPos = InstrB(nPosEnd, biData, CByteString("Content-Type:"))
                nPosBegin = nPos + 14
                nPosEnd = InstrB(nPosBegin, biData, CByteString(Chr(13)))

                oUploadFile.ContentType = CWideString(MidB(biData, nPosBegin, nPosEnd-nPosBegin))

                nPosBegin = nPosEnd+4
                nPosEnd = InstrB(nPosBegin, biData, vDataBounds) - 2
                oUploadFile.FileData = MidB(biData, nPosBegin, nPosEnd-nPosBegin)

                If oUploadFile.FileSize > 0 Then Files.Add LCase(sInputName), oUploadFile
            Else
                nPos = InstrB(nPos, biData, CByteString(Chr(13)))
                nPosBegin = nPos + 4
                nPosEnd = InstrB(nPosBegin, biData, vDataBounds) - 2
                If Not mcolFormElem.Exists(LCase(sInputName)) Then mcolFormElem.Add LCase(sInputName), CWideString(MidB(biData, nPosBegin, nPosEnd-nPosBegin))
            End If

            nDataBoundPos = InstrB(nDataBoundPos + LenB(vDataBounds), biData, vDataBounds)
        Loop
    End Sub

    'String to byte string conversion
    Private Function CByteString(sString)
        Dim nIndex
        For nIndex = 1 to Len(sString)
           CByteString = CByteString & ChrB(AscB(Mid(sString,nIndex,1)))
        Next
    End Function

    'Byte string to string conversion
    Private Function CWideString(bsString)
        Dim nIndex
        CWideString =""
        For nIndex = 1 to LenB(bsString)
           CWideString = CWideString & Chr(AscB(MidB(bsString,nIndex,1))) 
        Next
    End Function
End Class

Class UploadedFile
    Public ContentType
    Public FileName
    Public FileData
    Public FormElement

    Public Property Get FileSize()
        FileSize = LenB(FileData)
    End Property

    Public Sub SaveToDisk(sPath)
        Dim oFS, oFile
        Dim nIndex

        If sPath = "" Or FileName = "" Then Exit Sub
        If Mid(sPath, Len(sPath)) <> "\" Then sPath = sPath & "\"

        Set oFS = Server.CreateObject("Scripting.FileSystemObject")
        If Not oFS.FolderExists(sPath) Then Exit Sub

        Set oFile = oFS.CreateTextFile(sPath & FileName, True)

        For nIndex = 1 to LenB(FileData)
            oFile.Write Chr(AscB(MidB(FileData,nIndex,1)))
        Next

        oFile.Close
    End Sub

    Public Sub SaveToDatabase(ByRef oField)
        If LenB(FileData) = 0 Then Exit Sub

        If IsObject(oField) Then
            oField.AppendChunk FileData
        End If
    End Sub

End Class