Importazione file XLSX con DROPZONE

[max1974]

ragazzi sto cercando di importare un file XLSX con dropzone, ma non funziona ..... dove sbaglio ???
per me errore sta qui:
addedfile: function(file){ var data ="upload/" +file.name;var workbook = XLSX.readFile(data)}
ma non capisco quale errore sia...
grazie in anticipo.
ecco il codice html:

<div id="file-upload">
    <div class="panel panel-light">
        <div class="panel-heading">
            <div class="panel-title">
                <h4>Importa Dati Capitolati</h4>
            </div>
        </div>
        <div class="panel-body">
            <section>
              <div id="dropzone">
                <form class="dropzone needsclick" id="demoupload" action="/upload">
                  <div class="dz-message needsclick">
                      Trascina file qui o click per upload.<br>                      
                      <span class="note needsclick fa fa-download fa-4x" style="color:blue"></span>
                  </div>
                </form>
              </div>
            </section>
          <hr size="3" noshade color="#F00000">
          <div id="preview-template" style="display: none;">
            <div class="dz-preview dz-file-preview">
              <div class="dz-image"><img data-dz-thumbnail=""></div>
              <div class="dz-details">
                <div class="dz-size"><span data-dz-size=""></span></div>
                <div class="dz-filename"><span data-dz-name=""></span></div>
              </div>
              <div class="dz-progress"><span class="dz-upload" data-dz-uploadprogress=""></span></div>
              <div class="dz-error-message"><span data-dz-errormessage=""></span></div>
              <div class="dz-success-mark"></div>
              <div class="dz-error-mark"></div>
            </div>
          </div>          
        </div>
    </div>
</div>
    <div id="dvExcel">
    </div>

ecco il codice

  var dropzone = new Dropzone('#demoupload', {
              previewTemplate: document.querySelector('#preview-template').innerHTML,
              parallelUploads: 2,
              autoProcessQueue: false,
              thumbnailHeight: 120,
              thumbnailWidth: 120,
              maxFilesize: 3,
              validation: {
                   allowedExtensions: [".xls", ".html", ".xlsx"]
              },
              showFileList: false,
              addRemoveLinks: true,
              filesizeBase: 1000,
              dictRemoveFile:"Rimuovi File",
              thumbnail: function(file, dataUrl) {
                 if (file.previewElement) {
                     file.previewElement.classList.remove("dz-file-preview");
                     var images = file.previewElement.querySelectorAll("[data-dz-thumbnail]");
                     for (var i = 0; i < images.length; i++) {
                       var thumbnailElement = images[i];
                       thumbnailElement.alt = file.name;
                       thumbnailElement.src = dataUrl;
                     }
                     setTimeout(function() { file.previewElement.classList.add("dz-image-preview"); }, 1);
                   }
                 },
          addedfile: function(file){
            var data ="upload/" +file.name;                       
            var workbook = XLSX.readFile(data)
            var firstSheet = workbook.SheetNames[0];
            //Read all rows from First Sheet into an JSON array.
            var excelRows = XLSX.utils.sheet_to_row_object_array(workbook.Sheets[firstSheet]);
            //Create a HTML Table element.
            var table = $("<table />");
            table[0].border = "1";
            //Add the header row.
            var row = $(table[0].insertRow(-1));
            //Add the header cells.
            var headerCell = $("<th />");
            headerCell.html("CODICE");
            row.append(headerCell);
            var headerCell = $("<th />");
            headerCell.html("NOME");
            row.append(headerCell);
            var headerCell = $("<th />");
            headerCell.html("IMPORTO");
            row.append(headerCell);
            //Add the data rows from Excel file.
            for (var i = 0; i < excelRows.length; i++) {
                //Add the data row.
                var row = $(table[0].insertRow(-1));
                //Add the data cells.
                var cell = $("<td />");
                cell.html(excelRows[i].CODICE);
                row.append(cell);
                cell = $("<td />");
                cell.html(excelRows[i].NOME);
                row.append(cell);
                cell = $("<td />");
                cell.html(excelRows[i].IMPORTO);
                row.append(cell);
            }
            var dvExcel = $("#dvExcel");
            dvExcel.html("");
            dvExcel.append(table);
              }
           })