This is a snippet for a pattern I used to use when I iterate over an Array of objects applying a map async function but the process needs to be sync.

syncMapIterator.js

/**
 * Creates a new Sync MapIterator over objects with an asyncrhonus mapFunction
 * @param {[array]}   objects          [object array to iterate over]
 * @param {[Function]}   mapFunction [function to apply over each object sync mode]
 * @param {Function} done             [function to call when it's done]
 */
var SyncMapIterator = function(objects, mapFunction, done){
  this.objects = objects;
  this.i = 0;
  this.retries = 0;
  this.mapFunction = mapFunction;
  this.done = done;
};

SyncMapIterator.prototype.next = function(params) {
  var self = this;
  params = params || {};
  if(this.i>=this.objects.length){
    return this.done(params);
  }
  this.mapFunction(this.objects[this.i], params, function(newParams){
    self.i++;
    self.next(newParams);
  });
};

SyncMapIterator.prototype.hasNext = function(){
  return this.i < this.objects.length;
};

SyncMapIterator.prototype.retry = function(params) {
  this.i--;
  this.retries++;
  this.next(params);
};

module.exports = SyncMapIterator;

test.js

var SyncMapIterator = require('./syncMapIterator');

var map = new SyncMapIterator([5,4,3,2,1,0], function(value, params, callback){
  console.log('Waiting for ' + value + ' seconds..');
  setTimeout(function(){
    params.elements.push(value);
    callback(params);
  }, value*1000);
}, function(params){
  console.log(params);
  console.log('finished');
});

map.next({elements:[]});