How to show a block only after a specific post is reposted from a specific group and a person joins this group?

Question

JavaScript

Task:
There is a block with display; none.
After a person makes a repost of the post offered to him and joins this group, this block becomes visible.
Does anyone have a ready solution?

Answer 1

Through api vk
groups.getMembers - you get the last user of the group
wall.getById - you get the first entry on the user's wall (this should be a repost).
You compare, for example, the content or just the presence of a link to your domain.