simple promises implementation for fun

promises.js

function Promise () {
  var fail,then, instance, thenCb, failCb, self = this;

  self.resolve =  function (data) {
    if (thenCb) {
      thenCb(data);
    }
  };
  self.reject =  function (error) {
    if (failCb) {
      failCb(error);
    }
  };

  instance = {
    fail: function (cb) {
      failCb = cb;
      return self.get();
    },
    then: function (cb) {
      thenCb = cb;
      return self.get();
    }
  };

  self.get = function () {
    return instance;
  }
};

//example usage
var fs = require('fs');

function read (name) {
  var promise = new Promise();

  fs.readFile(name , function (error, data) {
    if (error) {
      promise.reject(error);
    }
    if (data) {
      promise.resolve(data);
    }
  });

  return promise.get();
};

read('viri.txt')
  .then(function (data) {
    console.log('wow i got data');
  })
  .fail(function () {
    console.log('shit failed')
  });