Promises using Q.

q_promise.js

var Q = require('q');

var async = function (prefix) {
  // create a promise wrapper
  var hold = Q.defer();
  var success = function () {
    var data = prefix + "SOLVED!";
    // by calling 'resolve', the next steps in the 
    // 'then' handler (e.g. 'console.log' below) 
    // will be executed with 'data' passed in
    hold.resolve(data);
  };
  // simulating an async call
  setTimeout(success, 100);
  // the promise object is returned immediately
  return hold.promise;
};

async('RE')
  .then(console.log);