Node.Js search and replace in files in directory recursively

gistfile1.txt

const fs = require('fs');
const path = require('path');


const walkSync = (dir, filelist = []) => {
	fs.readdirSync(dir).forEach(file => {
  
	  filelist = fs.statSync(path.join(dir, file)).isDirectory()
		? walkSync(path.join(dir, file), filelist)
		: filelist.concat(path.join(dir, file));
  
	});
  return filelist;
  }


  var elenco = walkSync("./public");  


  elenco.map(function(v, i, a) {
	fs.readFile(v, 'utf8', function (err, data) {

		console.log(v);

		var formatted = data.replace(/da sostituire/g, "con questo");
	  
	   	fs.writeFile(v, formatted, 'utf8', function (err) {
		  	if (err) return console.log(err);
	   	});
	  });

  })