NodeJs resize and optimize images with sharp

resize.js

const fs = require('fs');
const glob = require('glob');
const sharp = require('sharp');
const Promise = require('bluebird');

const successList = [];
const errorList = {};

glob("wp-content/uploads/**/*.+(jpeg|jpg)", function (er, files) {
  Promise.resolve(files)
    .mapSeries((file) => resize(file))
    .then(() => Promise.fromCallback(function(cb) {
        fs.writeFile('resize.log', JSON.stringify(errorList, null, 2) , cb);
      })
        .catch(function(err) {
          errorList['write_log_to_file_error'] = err;
        })
    )
    .then(function() {
      console.log('------------------------------');
      console.log('TOTAL:', files.length);
      console.log('OKAY:', successList.length);
      console.log('FAIL:', Object.keys(errorList).length);
    });
});

function resize(file) {
  return sharp(file)
    .resize(1920, 1440)
    .max()
    .withoutEnlargement()
    .toFormat('jpeg', { progressive: true, quality: 50 })
    .toBuffer()
    .then(buffer => Promise.fromCallback(cb => fs.writeFile(file, buffer, cb)))
    .then(function() {
      successList.push(file);
      console.log('Okay:', file);
    })
    .catch(function(err) {
      console.log('Fail:', file, '\n', err);
      errorList[file] = { message: err.message, fileName: err.fileName, lineNumber: err.lineNumber };
    });
}