function handleFilePickerChange(e) {
  const upload = AttachmentsCollection.insert(
    {
      file: e.target.files[0],
      chunkSize: 'dynamic',
    },
    false
  );

  upload.on('start', function () {
    console.log('Started upload');
  });

  upload.on('end', function (error, fileObj) {
    if (error) {
      console.log(`Error during upload: ${error}`);
    } else {
      console.log(`File "${fileObj.name}" successfully uploaded`);
    }
  });

  Tracker.autorun(() => {
    console.log(upload.progress.get());
  });

  upload.start();

  e.target.value = '';
}