phpjs/experimental/language/__DIR__.js

php.js offers community built php functions in javascript

function __DIR__() {
  // http://kevin.vanzonneveld.net
  // +   original by: Michael White (http://getsprink.com/)
  // -    depends on: dirname
  // -    depends on: __FILE__
  // %        note 1: Not a function in PHP, so in experimental
  // %        note 2: It will probably need a bit of work to make it fully
  // %        note 2: cross-browser but I tested it in FF3 and Safari 3 on
  // %        note 2: mac os x.
  // %        note 3: If the function thinks it is in the original HTML
  // %        note 3: document then the URL stored in this.window.location.href
  // %        note 3: is used. There might be a better choice for this.
  // %        note 4: I just upgraded to Safari 4 beta today and I found
  // %        note 4: that the method I used to get the current script tag
  // %        note 4: does not work for Safari 4.
  // %        note 4: In my local code I swapped out that part for Prototype's
  // %        note 4: $$('script') and everything worked fine again.
  // *     example 1: __DIR__();
  // *     returns 1: '/myDir'

  return this.dirname(__FILE__());
}