private data patterns in JS

gistfile1.js

// I saw this programming style somewhere a while back and liked it.

function PubSub(subject) {
  var observers = [];

  subject.notify = function() {
    for (var i = 0; i < observers.length; ++i) {
      try {
        observers[i].apply(null, arguments);
      } catch (e) {
        setTimeout(function() { throw e; }, 0);
      }
    }
  }
  
  subject.observe = function(obs) {
    observers.push(obs);
    return function removeObserver() {
      observers.splice(observers.indexOf(obs), 1);
    };
  }
}

function makeObject() {
  var obj = {};
  var notifyPending = null;
  
  function access(k, v) {
    if (arguments.length === 1) {
      return obj[k];
    } else {
      obj[k] = v;
      if (!notifyPending) {
        notifyPending = setTimeout(function() {
          notifyPending = null;
          access.notify();
        }, 0);
      }
    }
  }
  
  PubSub(access);
  
  return access;
}

var obj = makeObject();
obj('foo', 'bar');
obj('foo'); // => 'bar'

obj.observe(function() {

});

obj('baz', 'bleem');

function makeProperty(value, getter, setter) {
  
  function rawGet() { return value; }
  function rawSet(v) { value = v; }
  
  // could also have getter/setter as function factories
  if (!getter) getter = function(raw) { return raw(); };
  if (!setter) setter = function(raw, v) { return raw(v); };
  
  function property(v) {
    if (arguments.length === 0) {
      return getter(function() { return value; });
    } else {
      return setter(function(v) { value = v; }, v);
    }
  }
  
  return property;

}

function makeAttribute(value, getter, setter) {

  var pubsub = {};
  PubSub(pubsub);
  
  var notify = pubsub.notify;
  
  var property = makeProperty(value, getter, function(raw, v) {
    // ... mojo
    notify();
  });
  
  property.observe = pubsub.observe;
  
  return property;
  
}