A way to give existing callback-based libraries a chainable interface.

chaining.js

module.exports = Lib

function Lib() {
  this._queue = []
  var methods = ['one', 'two', 'three']
  methods.forEach(this._addMethod.bind(this))
}

Lib.prototype._addMethod = function (name) {
  var self = this
  this[name] = function (cb) {
    if (!cb) {
      self._queue.unshift({name: name})
    } else {
      self._queue.unshift({name: name})
      self._runQueue(cb)
    }
    return self
  }
}

Lib.prototype._runQueue = function (cb) {
  var self = this
  function run() {
    var next = self._queue.pop()
    if (next) self['_' + next.name](run)
    else cb(null)
  }
  run()
}

Lib.prototype._one = function (cb) {
  process.nextTick(function () {
    console.log('one')
    cb(null)
  })
}

Lib.prototype._two = function (cb) {
  process.nextTick(function () {
    console.log('two')
    cb(null)
  })
}

Lib.prototype._three = function (cb) {
  process.nextTick(function () {
    console.log('three')
    cb(null)
  })
}

var lib = new Lib()
lib.one()
   .two()
   .three(function () {
     console.log('ALL DONE');
   })