Best way to save a table human readable

Questions
3

I am going to try this now.

Is it even possible to save a local file in a subfolder on a HTML5 game? I have tried to use sys.get_save_file() but this seems to save files in the profile path of the user who is running the webserver, which is not always accessable for me.

When I try to use rxi.json for encoding my table as json I get the following error:

local file = sys.get_save_file("christmas_game_2018", "test.txt")
if not sys.save(file, json.encode(shared_data)) then
	pprint("Gamedata not saved")
end

ERROR:SCRIPT: /main/game.script:11: bad argument #2 to 'save' (table expected, got string)