ServiceNow cart API to request catalog item through script

var cart = new Cart();
var item = cart.addItem('12345678123456781234567812345678'); // sys id of the Catalog item
cart.setVariable(item, "employee", current.u_employee_name);
cart.setVariable(item, "employee_email", current.u_employee_email);
cart.setVariable(item, "employee_number", current.u_employee_number);
cart.setVariable(item, "termination_date", current.u_termination_date);
var rc = cart.placeOrder();