POS-Server/app/views/open_cash_registers/new.js.erb

$('#dialog h3.modal-title').html("Activar caja registradora");
 // Render the edit form
 $('.modal-body').html('<%= j render("open_cash_registers/form") %>');
 // Show the dynamic dialog
 $('#dialog').modal("show");

 	// Set focus to the first element
 	$('#dialog').on('shown.bs.modal', function () {
    $('.first_input').focus();
    $('#open_cash_register_cash_register_id').select2();
  });