Backup your tumblr!
[sudo] npm i tumblr-backup
Backup your blog first!
tumblr-backup hostname-or-cname where-to
Then you can browse your archive:
tumblr-backup serve where-to
Don't worry, everything is just json files and the related media (yes it downloads images etc too!)
In-progress: Version 2 which will bring a rewrite using tests and a lot more :) TODO: use grunt or something for building a deploy version w/browserify