nodejs chainging, whats going wrong

#!/usr/bin/env node

var fs = require('fs')

function Queue() {

  // store your callbacks
  this._methods = [];

  // keep a reference to your response
  this._response = null;

  // all queues start off unflushed
  this._flushed = false;
}



Queue.prototype = {

  // adds callbacks to your queue
  add: function(fn) {

    // if the queue had been flushed, return immediately
    if (this._flushed) {
      fn(this._response);

    // otherwise push it on the queue
    } else {

      this._methods.push(fn);
    }
  },



  flush: function(resp) {

    // note: flush only ever happens once
    if (this._flushed) {

      return;
    }

    // store your response for subsequent calls after flush(
    this._response = resp;

    // mark that it's been flushed
    this._flushed = true;

    // shift 'em out and call 'em back
    while (this._methods[0]) {

      this._methods.shift()(resp);
    }
  }
};


var foo = function(){

    this.method1 = function(){
        console.log('method1 called')
        return this
    }

    this.method2 = function(){
        fs.readFile('./lib/jsondb', function(){
            console.log('method2 called')
        })
        return this
    }

    this.method3 = function(){
        console.log('method3 called')
        return this
    }
}

var o = new foo()
var queue = new Queue()

var front = {

    "one" : function(){
        queue.add(o.method1)
        queue.flush()
        return this
    },

    "two" : function(){
        queue.add(o.method2)
        return this
    },
    "three" : function(){
        queue.add(o.method3)
        return this
    }
}

front.one()
    .two()
    .three()