HOW TO MAKE this possible? Help required

Need help. I'm looking something (be it plugins/script/anything) that can make this possible:

I want my visitor to do certain tasks & get points.

Example: fill up form = gets 10 points, fill survey = gets 20 points, share post on Facebook = 5 points.. These points will accumulate and can be used as an exchange for coupon/voucher etc...

Any existing script/plugin for this?

Can it be done with javascript?

Paid-to industry has plenty of these scripts.
Survey site scripts. Auroragpt(name probably change), etc.

If you had an already built site, it's not super super hard.
But you need to take precautions on the server side to very the incentivized actions actually happened.