const streamBuffers = require('stream-buffers');
const archiver = require('archiver');

const zipDir = (dir) => {
  const output = new streamBuffers.WritableStreamBuffer({
    initialSize: (100 * 1024),    // start at 100 kilobytes.
    incrementAmount: (10 * 1024), // grow by 10 kilobytes each time buffer overflows.);
  });
  const archive = archiver('zip');
  archive.on('end', () => {
    done(null, output);
  });
  archive.on('error', done);
  archive.pipe(output);
  archive.directory(dir, '/');
  archive.finalize();
};

zipDir(path.join(__dirname, 'path', 'to', 'directory'));