Lazy initialization with Object.defineProperty

lazy.js

var accessorDescriptor, valueDescriptor;

accessorDescriptor = {
  __proto__: null,
  get: null, set: null,
  enumerable: true,
  configurable: true
};

valueDescriptor = {
  __proto__: null,
  value: null,
  writable: true,
  configurable: true
};

function lazy(target, property, getter, options) {
  var writable, enumerable;

  if (!options) options = lazy.defaults;

  if ('writable' in options) writable = Boolean(options.writable);
  else writable = lazy.defaults.writable;

  if ('enumerable' in options) enumerable = Boolean(options.enumerable);
  else enumerable = lazy.defaults.enumerable;

  accessorDescriptor.get = accessorDescriptor.set = accessor;
  accessorDescriptor.enumerable = enumerable;

  return Object.defineProperty(target, property, accessorDescriptor);

  function accessor() {
    if (arguments.length) {
      if (writable) valueDescriptor.value = arguments[0];
      else return;
    } else {
      valueDescriptor.value = getter.call(this);
    }

    valueDescriptor.writable = writable;
    valueDescriptor.enumerable = enumerable;

    return Object.defineProperty(this, property, valueDescriptor)[property];
  }
}

lazy.defaults = {
  writable: false,
  enumerable: false
};

function bound(target, property, method, options) {
  return lazy(target, property, function () {
    return method.bind(this);
  }, options);
}