This code is a NetSuite Wizard or NetSuite Assistant which has a File Upload functionality.

netsuite_file_upload_wizard.js

/**
 * File Upload Wizard.
 * @param {nlobjRequest} request Request object
 * @param {nlobjResponse} response Response object
 * @returns {Void} Any output is written via response object
 */

function main(request, response) {
  var assistant = nlapiCreateAssistant("File Upload Wizard", true);
  assistant.setOrdered(true);

  /* VERY IMPORTANT - Client side script for this wizard must be included. */
  assistant.setScript('customscript_file_upload_wizard_css');

  assistant.addStep('custstep_file_upload', 'Upload File').setHelpText("Upload your file.");
  assistant.addStep('custstep_summary', 'Summary').setHelpText("Confirm details below.");

  if (request.getMethod() == 'GET') {
    if (!assistant.isFinished()) {
      if (assistant.getCurrentStep() == null)
        assistant.setCurrentStep(assistant.getStep("custstep_file_upload"));

      var step = assistant.getCurrentStep();

      if (step.getName() == "custstep_file_upload") {
        var fileField = assistant.addField('custpage_file', 'select', 'File');
        var uploadButton = assistant.addField('custpage_upload_btn', 'inlinehtml', 'Browse');
        var fileNameField = assistant.addField('custpage_file_name', 'text', 'File Name');

        fileField.setMandatory(true);
        fileField.setDisplayType('disabled');
        fileNameField.setDisplayType('hidden');

        /* This is the upload button markup. The button ID is browse (id="browse")*/
        uploadButton.setDefaultValue('<table id="custbl_button"> <tbody> <tr> <td> <table id="tbl_select" cellpadding="0" cellspacing="0" border="0" style="margin-left:32px; cursor:hand;"> <tbody> <tr id="tr_select" class="pgBntG"> <td id="tdleftcap_select"> <img src="/images/nav/ns_x.gif" class="bntLT" border="0" height="50%" width="3"> <img src="/images/nav/ns_x.gif" class="bntLB" border="0" height="50%" width="3"> </td> <td id="tdbody_select" height="20" valign="top" nowrap="" class="bntBgB"> <input type="button" style="" class="rndbuttoninpt bntBgT" value="Browse" id="browse" name="browse" onmousedown="this.setAttribute(\'_mousedown\',\'T\'); setButtonDown(true, true, this);" onmouseup="this.setAttribute(\'_mousedown\',\'F\'); setButtonDown(false, true, this);" onmouseout="if(this.getAttribute(\'_mousedown\')==\'T\') setButtonDown(false, true, this);" onmouseover="if(this.getAttribute(\'_mousedown\')==\'T\') setButtonDown(true, true, this);"> </td> <td id="tdrightcap_select"> <img src="/images/nav/ns_x.gif" height="50%" class="bntRT" border="0" width="3"> <img src="/images/nav/ns_x.gif" height="50%" class="bntRB" border="0" width="3"> </td> </tr> </tbody> </table> </td> </tr> </tbody> </table>');
      } else if (step.getName() == "custstep_summary") {
        var fileUploadStep = assistant.getStep('custstep_file_upload');
        var fileField = assistant.addField('custpage_file_review', 'text', 'File');

        fileField.setDisplayType('inline');
        fileField.setDefaultValue(fileUploadStep.getFieldValue('custpage_file_name'));
      }
    }

    response.writePage(assistant);
  } else {
    assistant.setError(null);

    if (assistant.getLastAction() == "finish") {
      assistant.setFinished("Your file has been processed.");
      assistant.sendRedirect(response);
    } else if (assistant.getLastAction() == "cancel") {
      nlapiSetRedirectURL('tasklink', "CARD_-29");
    } else {
      if (!assistant.hasError())
        assistant.setCurrentStep(assistant.getNextStep());

      assistant.sendRedirect(response);
    }
  }
}