gistfile1.js

function Promise(){
  this._callbacks = [];
}

Promise.prototype.resolve = function (data) {
  if (typeof this._data !== 'undefined') {
    // assuming console
    console.error('This promise has already been resolved');
    return;
  }

  this._data = data;

  // execute all currently attached callbacks
  while (this._callbacks.length) {
    this._callbacks.shift().call(null, data);
  }
}

Promise.prototype.success = function (cb) {
  // execute callback immediately if promise is resolved
  if (typeof this._data !== 'undefined') {
    cb.call(null, this._data);

  // otherwise store callback and wait
  } else {
    this._callbacks.push(cb);
  }
  
  // for chaining
  return this;
}