What am I supposed to study to achieve this? Yes, it's Javascript, but what exactly?

Trying to learn how to make something like this. In short, each card has a connector to their right, and the vertical line also has a divider. When I click each card, a line extend from the card connector to the divider connector, to the exact precise point. I get that it's Javascript, or some framework?, but I don't understand exactly which part of it. I have a basic understanding of Javascript just to do basic stuff, and I am not interested in master everything (like backend stuff), just not sure exactly where should I start to learn this,