This function is run when a user changes any of their core data to update duplicates across the database.

updateDuplicateData.js

/**
 * 'UpdateDuplicateData'
 * 
 * Used to update user data on all models that it is duplicated on
 * 
 * @param  {object}   User      The main user model
 * @param  {object}   changes   An object containing the changed user attributes
 * @param  {Function} cb        Callback - function(err){}
 * 
 */
exports.updateDuplicateData = function(userID, changes, cb){
  userID = String(userID);

  // I'm using async.js to run all the update functions in parrallel.
  // When all these functions have finished the master callback function
  // will be fired
  async.parallel({
 
    updateFeedItems: function(cb){ 

      // make empty object
      var mongoSet = {};
      
      // loop over each change and put it in the mongoSet object with 'user.'
      // prepended so that it'll work with the mongo update query.
      for(var prop in changes) mongoSet['user.' + prop] = changes[prop];

      // run the update query
      DB.model('feeditems')
      .update({'user._id': userID}, {'$set': mongoSet}, {multi: true}, cb);
    },

    updateComments: function(cb1){
      console.log('updating comments...');

      // run the update query
      DB.model('feeditems')
      .find({'comments.user._id': userID})
      .run(function(err, feeditems){
        if(err) return cb1(err);

        // if no feeditems found: return callback
        if(!feeditems.length) return cb1();

        //[Loop] over each feeditem
        async.forEach(feeditems, function(feeditem, cb2){ 

          //[Loop] over each of the feeditem's comments
          async.forEach(feeditem.comments, function(comment, cb3){
                 
            // if this isn't one of the user's comments: return
            if(String(comment.user._id) !== userID) return cb3();

            // extend the user object with the new changes
            myUtils.extend(comment.user, changes);

            //[Callback]
            cb3();

          // COMMENT LOOP FINISHED
          }, function(err){
            if(err) return cb2(err);

            //[Callback] save the feeditem
            feeditem.save(cb2);
          });

        // FEEDITEM LOOP FINISHED
        }, cb1);
      });
    }
  }, cb);
};