save-messages.js

export async function save(messages) {
  let db = await getDatabase();
  let fileId = prefs.getPrefs().id;

  let transaction = db.transaction(['messages'], 'readwrite');
  let objectStore = transaction.objectStore('messages');

  let promise = new Promise((resolve, reject) => {
    transaction.onerror = e => reject(e);
    transaction.oncomplete = e => resolve();
  });

  for (let message of messages) {
    message = {
      ...message,
      timestamp: message.timestamp.toString(),
      fileId
    };

    objectStore.put(message);
  }

  // Don't do anything if it fails
  try {
    await promise;
  } catch (e) {
    console.log('Error while saving web storage:', e);
  }
}