Combine multiple xlsx files with consistent structure into one

xlsx-combine.js

const xlsx = require('xlsx');

const glob = require('glob');

let result = [];

const readXlsx = (filePath) => {
  const wb = xlsx.readFile(filePath);

  for (let sheetName of wb.SheetNames) {
    const sheet = wb.Sheets[sheetName];
    const data = xlsx.utils.sheet_to_json(sheet);
    // console.log(data);
    result = [...result, ...data];
  }
};

const writeXlsx = (filePath) => {
  const workBook = xlsx.utils.book_new();
  const sheet = xlsx.utils.json_to_sheet(result);
  console.log(sheet);
  xlsx.utils.book_append_sheet(workBook, sheet, 'sheet1');
  xlsx.writeFile(workBook, filePath);
  // console.log(workBook);
};

glob('doc/**/*.xlsx', (error, files) => {
  console.log('files', files);
  for (let file of files) {
    console.log('file', file);
    readXlsx(file);
  }
  console.log('result', result);
  writeXlsx('./result.xlsx', (res) => {
    console.log(res);
  });
});