How would I use javascript to read and write to a google document?

So, say I have a main.html file and a view.html file. The pages are hosted on the same website. There is also a google doc that allows literally anyone to edit, even users not signed in.

The idea is that main.html has a selector of a few options. When a user looking at main.html presses any of the options, it write to the google doc the option that was pressed. When someone views/refreshes the view.html file, it should look at the google doc and display whatever is there to the user.

I have no clue how to do this, or even where to start. If someone else has any idea how this could possibly work, please let me know. Also keep in mind there is no backend, just the .html files with <script> tags.