nodejs callbackDriven vs node-async vs node-sync

getUserSummary_nodejs_async.js

function getUserSummary(userId, callback)
{
    async.parallel({
        
        user : function(callback) {
            db.users.findUserById(userId, callback)
        },
        
        tweets : function(callback) {
            db.users.getTweets(userId, callback)
        },
        
        getFollowers : function(callback) {
            db.users.getFollowers(userId, callback)
        },
        
        getFollowing : function(callback) {
            db.users.getFollowing(userId, callback)
        }
        
    }, callback)
}

getUserSummary_nodejs_classic.js

function getUserSummary(userId, callback)
{
    db.users.findUserById(userId, function(err, user){
        if (err) return callback(err);
        
        db.users.getTweets(userId, function(err, tweets){
            if (err) return callback(err);
            
            db.users.getFollowers(userId, function(err, followers){
                if (err) return callback(err);
                
                db.users.getFollowing(userId, function(err, following){
                    if (err) return callback(err);
                    
                    callback(null, {
                        user : user,
                        tweets : tweets,
                        followers : followers,
                        following : following
                    })
                })
            })
        })
    })
}

getUserSummary_nodejs_sync.js

var getUserSummary = function(userId)
{
    return {
        user : db.users.findUserById(userId),
        tweets : db.users.getTweets(userId),
        followers : db.users.getFollowers(userId),
        following : db.users.getFollowing(userId)
    }
    
}.async()

getUserSummary_nodejs_sync_parallel.js

var getUserSummary = function(userId)
{
    var dbUsers = db.users;
    
    var user = dbUsers.findUserById.future(dbUsers, userId),
        tweets = dbUsers.getTweets.future(dbUsers, userId),
        followers = dbUsers.getFollowers.future(dbUsers, userId),
        following = dbUsers.getFollowing.future(dbUsers, userId);
    
    return {
        user : user.result,
        tweets : tweets.result,
        followers : followers.result,
        following : following.result
    }
    
}.async()