I am trying to pre-fill the values on the bigCommerce checkout page. As the checkout page uses embedded react, that's why I am unable to change the field values with plain javascript methods. Although, I am able to change the values using Document.execCommand(). Here is the actual code for changing the first name:

  document.getElementById("firstNameInput").focus();
  document.execCommand("insertText", false, customerInfo.firstName);

But the problem is that I am unable to change/select country from the dropdown menu using Document.execCommand().

So my question is that, how can I change the dropdown value using document.execCommand?

PS: I know that document.execCommand is deprecated, but I don't have any alternate method available right now to change the values because as I said, plain javascript methods does not change the field values on bigcommerce checkout page.