I do have an existing spreadsheet for the task, which is being used right now without any client.
I would like for my client to read format information (background color) and edit cell values, which I can get to work.
The problem is that my users don't necessarily have a google account, with which they could authenticate themselves. So all the examples on the google site don't cover my use case.
How can I avoid authentication (the spreadsheet is public) while reading format information and edit cell values with my JavaScript app (which is targeted to be a Cordova App)?