Deep Extend for JavaScript

Object.deepExtend.js

//http://andrewdupont.net/2009/08/28/deep-extending-objects-in-javascript/
Object.deepExtend = function(dst, src) {
  for (var prop in src) {
    if (src[prop] && src[prop].constructor && src[prop].constructor === Object) {
      dst[prop] = dst[prop] || {};
      arguments.callee(dst[prop], src[prop]);
    } else {
      dst[prop] = src[prop];
    }
  }
  return dst;
};