An interesting way to share private state across components of modules in JavaScript:
(credit goes to this article)

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var module = (function (module) {
  var _private = module._private = module._private || {};
  var _seal = module._seal = module._seal || function () {
    delete module._private;
    delete module._seal;
    delete module._unseal;
  }
  var _unseal = module._unseal = module._unseal || function () {
    module._private = _private;
    module._seal = _seal;
    module._unseal = _unseal;
  };
  // permanent access to _private, _seal, and _unseal

  return module;
}(module || {}));

_unseal must be called by a function (probably some sort of loader function) that was initialized before _seal was called (so that _unseal will be present in its closure scope).

For example:

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var loadScript = function (scriptUrl) {
  module._unseal();
  var script = document.createElement('script');
  script.src = scriptUrl;

  if (script.readyState) {
    script.onreadystatechange = function () {
      if (script.readyState === "loaded" ||
          script.readyState === "complete") {
        script.onreadystatechange = null;
        module._seal();
      }
    };
  }
  else {
    script.onload = function() {
      module._seal()
    };
  }

  document.getElementsByTagName('head')[0].append(script);
};