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>