Why do banks payment validation systems use JavaScript redirects

Question

When you pay through online payment systems ( being with or without 3DSecure), you fill in the form and validate, and from a strictly visual point of view, things seems pretty straightforward. But behind, there is often multiple redirections, which are handled through JavaScript.

Basically, your data is submitted, and you land on a page with a pre-filled form, which is immediately submitted through JavaScript, sometimes multiple times in a row (with fast enough connection, you don't even see those steps from browser).

I was wondering why they do it that way (instead of proper back-end redirections), and I can't find an answer to it. My guess is that it's just to make it harder for scripts to follow it, but it's still possible to do it (so why bother), and to my opinion, the "dirty aspect" of it (from a coder point of view) is not worth the constraints it gives to scripts that would attempt an automatic validation.

Do you have any insights on this?

Answer 1

From my view, using the JavaScript will detect the bot or human efficiently.

As you can already saw, how the Google validate the bot.

It's just simple a check box, but it's quite complicated if you try to write the bot to verify or pass the check. (Now I still don't know how to pass by it ^)