window.fbAsyncInit = function() {
    FB.init({ appId: 'your app id', status: true, cookie: true,
        xfbml: true
    });
};
(function() {
    var e = document.createElement('script'); e.async = true;
    e.src = document.location.protocol +
          '//connect.facebook.net/en_US/all.js';
    document.getElementById('fb-root').appendChild(e);
} ());