How to use the pouchdb-binary-utils.readAsArrayBuffer function in pouchdb-binary-utils

function appendBlob(buffer, blob, start, end, callback) {
  if (start > 0 || end < blob.size) {
    // only slice blob if we really need to
    blob = sliceBlob(blob, start, end);
  }
  readAsArrayBuffer(blob, function (arrayBuffer) {
    buffer.append(arrayBuffer);
    callback();
  });
}

err.code = 'ETIMEDOUT';
      } else if (typeof xhr.response === 'string' && xhr.response !== '') {
        try {
          err = JSON.parse(xhr.response);
        } catch (e) {}
      }

      err.status = xhr.status;

      callback(err);
    }
    cleanUp();
  };

  if (options.body && (options.body instanceof Blob)) {
    readAsArrayBuffer(options.body, function (arrayBuffer) {
      xhr.send(arrayBuffer);
    });
  } else {
    xhr.send(options.body);
  }

  return ret;
}