If a user wants to verify the payouts, they need to download the code and run it, yes. They can play the game without verifying the payouts though. I just need to provide a mechanism for users to verify the fairness if they wish to...
I'm not trying to discourage you or conclude it is not provable fair.I'm an avid JavaScript developer and I know what problems it may give when you leave the verification part to the script.The easiest way I could have made it possible is by providing a space for user to verify the script.He inputs the initial values or whatever the lottery suggests, and have them run through my server or console and give users the updated modified value.If users doubt the value isn't true, they can always run the script locally and get the same data.