$('#button-login').on('click', function (e) {
  e.preventDefault();

  FB.login(function (response) {
    if (response.status === 'connected') {
      // the user is logged in and has authenticated your app
      var userId = response.authResponse.userID;
      var accessToken = response.authResponse.accessToken;

      $('<form>', {
        'action': '/login',
        'method': 'post',
        'html': '<input type="hidden" name="accessToken" value="' + accessToken + '" />'
      }).appendTo(document.body).submit();
    } else if (response.status === 'not_authorized') {
      // ths user is logged into Facebook, but has not authenticated your app
    } else {
      // the user isn't logged into Facebook
    }
  }, { scope: 'public_profile, email' });
});