Function binding with Async.

index.js

var async = require('async');

//
// Constructor function.
//
function Test() {}

//
// Start the async operation.
//
//    This isn't the best example, but shows how you can scope
//    function calls in async without using `var self = this;`
//
//    Output: `{ '0': null, '1': [ 'one', 'two' ] }`
//
Test.prototype.go = function() {
  async.series([
    function(fn) {
      return this.one(fn);
    }.bind(this),
    function(fn) {
      return this.two(fn);
    }.bind(this),
  ],
  function() {
    console.log(arguments);
  });
};

//
// Simulated async operations
// ==========================
//

//
// One.
//
Test.prototype.one = function(fn) {
  return fn(null, 'one');
};

//
// Two.
//
Test.prototype.two = function(fn) {
  return fn(null, 'two');
};

//
// Instantiate a new Test object then start the async operation.
//

var test = new Test();
test.go();