I'm finishing another HTML5 game, and this time I'd like to do some spying business on the players... Mostly just basic stuff: when they are playing, for how long, what upgrades they are buying the most and so on. Now, my first idea was just to collect this information during the gameplay, and then have a Javascript function fire when they close the tab/browser, and said function would send it to my server via Socket.io. This, of course, wouldn't work, because anyone who takes a look at the code would realize it and could start sending a tonne of false info which would mess up my statistics.

Questions:

• Is there a way to effectively do this?
• If yes, what kind of info should I be looking for, aside from stuff I already mentioned?