combine multiple xlsx files in a directory and save them into one file

combine.js

var xlsx = require("xlsx");
var fs = require("fs");

function readFileToJson(filename) {
  var wb = xlsx.readFile(filename);
  var firstTabName = wb.SheetNames[0];
  var ws = wb.Sheets[firstTabName];
  var data = xlsx.utils.sheet_to_json(ws);
  return data;
}

var target_dir = __dirname + "/files";
var files = fs.readdirSync(target_dir);
console.log(files);

var combinedData = [];

files.forEach(function(file) {
  var data = readFileToJson(`./files/${file}`);
  combinedData = combinedData.concat(data);
});

var newWB = xlsx.utils.book_new();
var newWS = xlsx.utils.json_to_sheet(combinedData);
xlsx.utils.book_append_sheet(newWB, newWS, "urls data");
xlsx.writeFile(newWB, "newCombinedData.xlsx");
console.log("Done");