Mark code 2

synchronousAndUgly.js

// User ID
var _id;

// Facebook ready
window.fbAsyncInit = function() {
    FB.init({ appId: 'XXX' });
    
    // Do we have a user?
    FB.getLoginStatus(function(response) {
        if('connected' === response.status) {
            // Save user ID
            _id = response.authResponse.userID;

            // NOTE: nest all dependencies, not good for performance and readability
            get('anotherLibrary.js', function() {
                if(anotherLibrary.success) {
                    get('yetAnotherLibrary.js', function() {
                        if(yetAnotherLibrary.status) {
                            // Done, now get user from Kinvey
                            kinvey.user.fetch(_id, function(user) {
                                // User found, go ahead and render page
                            });
                        }
                    });
                }
            });
        }
    });
};