text: var XLSX = Npm.require('xlsx');
  var XLS = Npm.require('xlsjs');
  
  Workbook = function (fileType) {
    this.fileType = fileType;
  
    this.SheetNames = [];
    this.Sheets = {};
  };
  
  Workbook.prototype.addSheet = function (sheetName, sheet) {
    this.SheetNames.push(sheetName);
    this.Sheets[sheetName] = sheet;
  };
  
  Workbook.prototype.writeToFile = function (filePath) {
    if (this.fileType === 'xlsx') {
      return XLSX.writeFile(this, filePath);
    }
    else if (this.fileType == 'xls') {
      return XLS.writeFile(this, filePath);
    }
  };
  
  Workbook.prototype.write = function (wopts) {
      if (this.fileType === 'xlsx') {
          return XLSX.write(this, wopts);
      }
      else if (this.fileType == 'xls') {
          return XLS.write(this, wopts);
      }
  };