after.js

var async = require('async');

function getUserFriends(userName, next) {
    var s = {}

    db.users.findOne({name:userName}, foundUser);

    function foundUser(err, user) {
        if (err != null) return next(err);
        s.user = user
        getFriendsById(s.user.id, gotFriends);
    }

    function gotFriends(err, friends) {
        if (err != null) return next(err);
        s.friends = friends
        if (s.user.type == 'power user') {
            async.map(s.friends, getFriendsById, wtfFriendAction);
        } else {
            return next(null, s.friends);
        }
    }

    function wtfFriendAction(err, friendsOfFriends) {
        for (var i = 0; i < friendsOfFriends.length; i++) {
            for (var j = 0; j < friendsOfFriends[i].length; j++) {
                if (s.friends.indexOf(friendsOfFriends[i][j]) != -1) {
                    s.friends.push(friendsOfFriends[i][j]);
                }
            }
        }
        return next(null, s.friends);
    }
}

function getFriendsById(userId, next) {
    db.friends.find({userId:userId}, function (err, friends) {
        if (err != null) return next(err);
        return next(null, friends);
    });
}

before.js

var async = require('async');

var getUserFriends = function (userName, next) {
    db.users.findOne({name:userName}, function (err, user) {
        if (err != null) return next(err);
        getFriendsById(user.id, function (err, friends) {
            if (err != null) return next(err);
            if (user.type == 'power user') {
                async.map(friends, getFriendsById, function (err, friendsOfFriends) {
                    for (var i = 0; i < friendsOfFriends.length; i++) {
                        for (var j = 0; j < friendsOfFriends[i].length; j++) {
                            if (friends.indexOf(friendsOfFriends[i][j]) != -1) {
                                friends.push(friendsOfFriends[i][j]);
                            }
                        }
                    }
                    return next(null, friends);
                });
            } else {
                return next(null, friends);
            }
        });
    });
}
var getFriendsById = function (userId, next) {
    db.friends.find({userId:userId}, function (err, friends) {
        if (err != null) return next(err);
        return next(null, friends);
    });
}