Node.js zip archiver

zip.js

#!/usr/bin/env node
'use strict';
const _ = require('lodash');
const filepath = require('filepath');
const Promise = require('bluebird');
const Archiver = require('archiver');

const output = filepath.create(process.env.OUTPUT).newWriteStream();
const archive = Archiver('zip');

output.on('close', function() {
  console.log(archive.pointer() + ' total bytes');
  console.log('archiver has been finalized and the output file descriptor has closed.');
});

archive.on('error', function(err) {
  throw err;
});

archive.pipe(output);

const directory = filepath.create(process.env.INPUT);

function relativeBasename(file) {
  return _.difference(file.path.split('/'), directory.path.split('/')).join('/');
}

function appendFiles(archive, files) {
  const promises = [];
  for(let file of files) {
    if (file.isDirectory()) {
      promises.push(appendFiles(archive, file.list()));
    } else {
      promises.push(Promise.resolve(archive.append(file.newReadStream(), { name: relativeBasename(file) })));
    }
  }
  return Promise.all(promises);
}

Promise.resolve(directory.list())
  .then(files => {
    return appendFiles(archive, files);
  })
  .then(() => {
    archive.finalize();
  });