code: function(src_excel_file, dest_dir, head, separator) {
  
          arraySeparator = separator;
  
          if (!fs.existsSync(dest_dir)) {
              fs.mkdirSync(dest_dir);
          };
          console.log("parsing excel:", src_excel_file);
          var excel = xlsx.parse(src_excel_file);
          _toJson(excel, dest_dir, head);
      }
docs: export .xlsx file to json
  src_excel_file: path of .xlsx files.
  dest_dir: directory for exported json files.
  head: line number of excell headline.
  separator : array separator.