How to have 2 modals on one button with a condition in the order of displaying?

Question

I am making a shopping site that by pressing purchase button ....with two modals on only one button user should know that he should first select a size from dropdown form (in a modal) if he selected, the second modal which is added to basket should be displayed.

Answer 1

Add a class to the button on the first click (or some other known user activity). Check the presence of this class inside onclick in order to change the button behavior. Use css to change the button.