Sharepoint 2016. Change custom upload location to current document set

Question

I have implemented a custom upload button on a modified 'docsethomepage.aspx'. The new page shows the properties of the DS.

I would like using javascript to upload the file to this Doc set instead to the Documents Folder.

I am following the great help found in here I would 'only' need to change the path from Documents to this Docucment Set. The Query Strings in the URL have these IDs available:

ID, FolderCTID, List and RootFolder of which I suspect need to use.

I am trying to fiddle with the uploadFile function but so far failed. Your help much appreciated.

Code:

 <script language="javascript" type="text/javascript">  

  var fileInput ;  

        $(document).ready(function()  
        {  
            fileInput = $("#getFile");  
            SP.SOD.executeFunc('sp.js', 'SP.ClientContext', registerClick);  
        });  
  
        function registerClick()  
        {  
            //Register File Upload Click Event  
            $("#addFileButton").click(readFile);  
        }  
        var arrayBuffer;  
  
        function readFile()  
        {  
            //Get File Input Control and read th file name  
            var element = document.getElementById("getFile");  
            var file = element.files[0];  
            var parts = element.value.split("\\");  
            var fileName = parts[parts.length - 1];  
            //Read File contents using file reader  
            var reader = new FileReader();  
            reader.onload = function(e)  
            {  
                console.log(e.target);
                console.log(fileName);
                uploadFile(e.target.result, fileName);  
            }  
            reader.onerror = function(e)  
            {  
                alert(e.target.error);  
            }  
            reader.readAsArrayBuffer(file);  
        }  
        var attachmentFiles;  
  
        function uploadFile(arrayBuffer, fileName)  
        {  
            //Get Client Context,Web and List object.  
            var clientContext = new SP.ClientContext();  
            var oWeb = clientContext.get_web();  
            var oList = oWeb.get_lists().getByTitle('Documents');  
            //Convert the file contents into base64 data  
            var bytes = new Uint8Array(arrayBuffer);  
            var i, length, out = '';  
            for (i = 0, length = bytes.length; i < length; i += 1)  
            {  
                out += String.fromCharCode(bytes[i]);  
            }  
            var base64 = btoa(out);  
            //Create FileCreationInformation object using the read file data  
            var createInfo = new SP.FileCreationInformation();  
            createInfo.set_content(base64);  
            createInfo.set_url(fileName);  
            //Add the file to the library  
            var uploadedDocument = oList.get_rootFolder().get_files().add(createInfo)  
            //Load client context and execcute the batch  
            clientContext.load(uploadedDocument);  
            clientContext.executeQueryAsync(QuerySuccess, QueryFailure);  
        }  
  
        function QuerySuccess()  
        {  
            console.log('File Uploaded Successfully.');  
        }  
  
        function QueryFailure(sender, args)  
        {  
            console.log('Request failed with error message - ' + args.get_message() + ' . Stack Trace - ' + args.get_stackTrace());  
        }  
    </script>