Done();

app.js

'use strict';

var util = require('util');

var randomInt = function (low, high) {
  return Math.floor(Math.random() * (high - low) + low);
};

var find = function (key, object, callback) {
  object.forEach(function (element) {
    setImmediate(function () {
      if (element.key === key) {
        callback(null, true, element.val);
      } else {
        callback(new Error('Key not found!'), false);
      }
    });
  });
};

var getValue = function (key, obj, callback) {
  var delay = randomInt(300, 1500);
  console.log('Start getVal "' + key + '", delay ' + delay + 'ms');
  setTimeout(function () {
    // Find key there
    find(key, obj, function (err, result, val) {
      if (result) {
        callback(null, val);
      } else {
        console.error(err);
      } });
  }, delay);
  console.log('End getVal "' + key + '", delay ' + delay + 'ms');
};

var getKey = function (map, callback) {
  var keys = Object.keys(map);
  keys.forEach(function (key) {
    callback(null, key);
  });
};
                       
var transformAsync = function (objects, map, callback) {
  var counter = 1;

  console.log('Function transformAsync is started.');
  console.log('-----------------------------------');
  getKey(map, function (err, key) {
    counter++;
    if(typeof map[key] === 'object') {
      getKey(map[key], function (err, nestedKey) {
        getValue(map[key][nestedKey], objects, function (err, value) {
          map[key][nestedKey] = value;
          if (--counter === 0) callback(null, map);
        });
      });
    } else {
      getValue(map[key], objects, function (err, value) {
        console.log('Key is: "%s", Value is: "%s"',key, value);
 
        map[key] = value;
        if (--counter === 0) callback(null, map);
      });
    }
  });
  console.log('--------------------------------------');
  console.log('Function async is ended.');
};

transformAsync(require('./data.json'), require('./map.json'), function (err, map) {
  console.log(util.inspect(map, {depth: null}));
  console.log('SUCCESS!');
});