Node style callbacks to q promises

q.js

var Q = require('q');
var assert = require('assert');

// Node style callback
function echo(thing, callback) {
  callback(null, thing + thing);
}

//
// Test code
// -------------------------------------

// Standard node version
echo('hello', function(err, result) {
  assert.strictEqual(result, 'hellohello');
  console.log('good');
});

// Using the `call` promise approach
Q.nfcall(echo, 'there').then(function(result) {
  assert.strictEqual(result, 'therethere');
  console.log('good');
}).fail(function(err) {
  console.log(err);
});

// Creating a reusable promise wrapper
var echoPromised = Q.denodeify(echo);

echoPromised('sir').then(function(result) {
  assert.strictEqual(result, 'sirsir');
  console.log('good');
}).fail(function(err) {
  console.log(err);
});