Rails 6 Create new record and print to printer after comfirmation

I have this form_with that creates a new record Post. I am trying to open the print window when the user clicks on the submit button. If rails predicts it should be something like adding onconfirm:printpage() to the Submit button but I cant seem to find how to do it.

= form.submit data: { disable_with: false, confirm: "Are you sure?" onconfirm: printpage() }

and then:

function printpage(){
  window.print()
}

I think you can do just like this:-

= form.submit, :class => "form_submit" ## add class to submit button

:javascript
  $(document).ready(function () { 
    $("#submit").click(function(event) {
      if( !confirm('Are you sure that you want to submit the form') ){
        event.preventDefault();
       }else{
        window.print(); 
        $('#myForm').submit(); ## your form id
       }
    });  
  });