I use Filesaver.js in my Chrome extension to download a backup of the archive as a txt file.
Quoting from its README file:
FileSaver.js is the solution to saving files on the client-side, and is perfect for webapps that need to generate files, or for saving sensitive information that shouldn't be sent to an external server.
FileSaver.js GitHub: https://github.com/eligrey/FileSaver.js/