post_file.js

  _onFileChanged(e) {
    let f = new FormData();

    // TODO set the attribute name
    f.append('video[video]', e.target.files[0]);

    var xhr = new XMLHttpRequest();
    xhr.addEventListener("load", () => {
      xhr.complete = true;
      // TODO Next action
    });
    xhr.addEventListener('progress', (evt) => {
      if (evt.lengthComputable) {
        let percentComplete = (evt.loaded / evt.total) * 100.0;
        logger.debug(`Upload status: ${percentComplete}%`);
        // TODO update progress bar
      }
    });

    xhr.open("POST", '/videos.json', true);
    xhr.responseType = 'json';
    xhr.setRequestHeader('X-CSRF-Token', $('meta[name=csrf-token]').attr('content'));
    xhr.send(f);
  }