What happens here in the background? I can imagine at the frontend you have some JavaScript, where an input field gets filled in or something. There has to be

What happens here in the background? I can imagine at the frontend you have some JavaScript, where an input field gets filled in or something. There has to be some server side checking as well, otherwise a simple HTTP POST would submit fine. I do like the idea, but if you need JavaScript anyway, why not have some invisible inputs. They work for now.