Implementing Gray World in Javascript

I am trying to implement the Gray World algorithm in Javascript. I am going to use a third party library like fabric.js. But everything I need to know about this algorithm.

After going through google I got Link1 , Wikipedia and using CPP . But I don't know about this algorithm. If I got this with an example, then I'm sure I can implement it.

Can someone please give some details with an example. It will be very helpful for me.