Current version have only add to cart that mean Buy now button function only for real product.
My customer want to add product to cart without  go to cart page  when click by using ajax like add some promotion to cart,
Can you add ajax add to cart and buy now button function for real product
Regard

Button can remain same, you just need jQuery functions to process update of cart on background

I have been completed it but it should be has default function in this plugin.
Regard

It is just your customer request, does not mean it should be in plugin.
But I understand your point of view.