How to make custom error handler in sale.order.ajax.js?

Question

1C-Bitrix

Hello. I'm doing checkbox processing in checkout. sale.order.ajax.
I use the article
https://mit24.ru/articles/gotovim-shtatnoe-oformle...
Only I have a little different

initAdditionalOptions: function() {
  var fz = BX('mitFZ');
  this.controlAdditionalOptions();
  BX.bind(fz, 'change', BX.proxy(this.controlAdditionalOptions, this));
},

controlAdditionalOptions: function() {
  var fz = BX('mitFZ');

  if (fz.checked == true) {
    BX.bind(this.orderSaveBlockNode.querySelector('a'), 'click', BX.proxy(this.clickOrderSaveAction, this));				
    BX.bind(this.totalBlockNode.querySelector('a'), 'click', BX.proxy(this.clickOrderSaveAction, this));
    BX.bind(this.mobileTotalBlockNode.querySelector('a'), 'click', BX.proxy(this.clickOrderSaveAction, this));
    BX.bind(this.totalInfoBlockNode.querySelector('a'), 'click', BX.proxy(this.clickOrderSaveAction, this));
    
  }
  else {
    BX.unbind(this.orderSaveBlockNode.querySelector('a'), 'click', BX.proxy(this.clickOrderSaveAction, this));
    BX.unbind(this.totalBlockNode.querySelector('a'), 'click', BX.proxy(this.clickOrderSaveAction, this));
    BX.unbind(this.mobileTotalBlockNode.querySelector('a'), 'click', BX.proxy(this.clickOrderSaveAction, this));
    BX.unbind(this.totalInfoBlockNode.querySelector('a'), 'click', BX.proxy(this.clickOrderSaveAction, this));

  }
}

I can’t output errors (I don’t understand which function to write where. Help, pliz.