How to set up the goal - clicking on the "Buy" button?

Question

Google Analytics

There is a site with a single button to buy. When you click on it, we go to the LiqPay form http://my site/liqpay/form199.php which is redirected to the payment system website.
Yandex Metrica does not want to consider the transition to the above link as a "page visit". Probably, it is necessary through JavaScript event.
How to track button clicks to track conversions? I ask for the finished code and advice on where to insert it

Answer 1

1. Set up a JavaScript goal in Yandex.Metrica
2. Paste the code inside the form code . Note that the identifier (in the MAIN_QUESTION example) must match both in the target and in the code.