<fb:login-button
id="facebook-login-button"
style="display:none"
scope="public_profile,email"
onlogin="facebookCheckLogin();">
</fb:login-button>

<button
id="facebook-logout-button"
style="display:none"
onclick="facebookLogout(this);">
Logout
</button>

<script>
    window.fbAsyncInit = function() {
        FB.init({
            appId            : '{{ ADD YOUR APP ID HERE}}',
            autoLogAppEvents : true,
            xfbml            : true,
            version          : 'v2.10'
        });
        FB.AppEvents.logPageView();

        FB.getLoginStatus(function(response) {
            if (response.authResponse && response.authResponse.accessToken) {
                document.getElementById('facebook-logout-button').style.display = "block";
            } else {
                document.getElementById('facebook-login-button').style.display = "block";
            }

            return response;
        });
    };

    function facebookLogout(_this) {
        _this.innerText = "Please wait.."
        return FB.logout(function(response) {
            window.location.reload();
        });
    }

    function facebookCheckLogin() {
        return FB.login(function(response) {
            if (response.authResponse && response.authResponse.accessToken) {
                window.location.reload();
            } else {
                alert("Looks like you didn't validate with facebook!");
            }
        }, {scope: 'public_profile,email'});
    }

    (function(d, s, id){
        var js, fjs = d.getElementsByTagName(s)[0];
        if (d.getElementById(id)) {return;}
        js = d.createElement(s); js.id = id;
        js.src = "//connect.facebook.net/en_US/sdk.js";
        fjs.parentNode.insertBefore(js, fjs);
    }(document, 'script', 'facebook-jssdk'));
</script>