FAPI.UI.showPayment -> API_callback why doesn't work?

Question

Classmates

Hello! I have a question. As I understood from the documentation, on the side of my application I write the following method

const API_callback = function(method, result, data) {
  console.log('API callback');
};

window.API_callback = API_callback;

After working out the showPayment function, namely, just close by the button or after the payment is completed and closed by the button, OK should pull my API_calback. The question is, why does my method not pull on any closing of the modal OK?