I can do logout but at that time localhost cookies folder are not clear that's why my site user is not logout properly.
<li>
       <button id="btnLogoff" onclick="deleteAllCookies()">LOGOFF / logout</button>
  </li>
 <script>
                            function deleteAllCookies() {
                                var cookies = document.cookie.split(";");
                                for (var i = 0; i < cookies.length; i++) {
                                    var cookie = cookies[i];
                                    var eqPos = cookie.indexOf("=");
                                    var name = eqPos > -1 ? cookie.substr(0, eqPos) : cookie;
                                    document.cookie = name + "=;expires=Thu, 01 Jan 1970 00:00:00 GMT";
                                }
                            }
                        </script>
 
     
    