This code was something I quickly put together to archive over 5000 text messages in Google Messages. I have no idea if Google frowns on this or not, but it's basically the same as if a human sat there and archived all the messages by hand.
Tested and working as of Monday, November 4, 2019.
- Sign into https://messages.google.com/web/
- Open Chrome Developers console by going to
View>Developer>JavaScript Console. - Copy and paste the code below into console. It should automatically run.