Login with FaceBook

   <script type="text/javascript">
       // Load the SDK Asynchronously
       (function (d) {
           var js, id = 'facebook-jssdk', ref = d.getElementsByTagName('script')[0];
           if (d.getElementById(id)) { return; }
           js = d.createElement('script'); js.id = id; js.async = true;
           js.src = "//connect.facebook.net/en_US/all.js";
           ref.parentNode.insertBefore(js, ref);
       } (document));

       // Init the SDK upon load
       window.fbAsyncInit = function () {
           FB.init({
               appId: '198191300293654', // App ID
               channelUrl: '//' + window.location.hostname + '/channel', // Path to your Channel File
               status: true, // check login status
               cookie: true, // enable cookies to allow the server to access the session
               xfbml: true  // parse XFBML
           });

           // listen for and handle auth.statusChange events
           FB.Event.subscribe('auth.statusChange', function (response) {
               if (response.authResponse) {
                   // user has auth'd your app and is logged into Facebook
                   FB.api('/me', function (me) {
                       if (me.name) {
                           document.getElementById('auth-displayname').innerHTML = me.name;
                       }
                   })
                   document.getElementById('auth-loggedout').style.display = 'none';
                   document.getElementById('auth-loggedin').style.display = 'block';
               } else {
                   // user has not auth'd your app, or is not logged into Facebook
                   document.getElementById('auth-loggedout').style.display = 'block';
                   document.getElementById('auth-loggedin').style.display = 'none';
               }
           });
           $("#auth-logoutlink").click(function () { FB.logout(function () { window.location.reload(); }); });
       }
</script>
<h1>
Facebook Login Authentication Example</h1>
<div id="auth-status">
<div id="auth-loggedout">

<div class="fb-login-button" autologoutlink="true" scope="email,user_checkins">Login with Facebook</div>
</div>
<div id="auth-loggedin" style="display: none">
Hi, <span id="auth-displayname"></span>(<a href="#" id="auth-logoutlink">logout</a>)
</div>
</div>