[KosBeg]

function extend() {
  var a = arguments, target = a[0] || {}, i = 1, l = a.length, deep = false, options;

  if (typeof target === 'boolean') {
    deep = target;
    target = a[1] || {};
    i = 2;
  }

  if (typeof target !== 'object' && !isFunction(target)) target = {};

  for (; i < l; ++i) {
    if ((options = a[i]) != null) {
      for (var name in options) {
        var src = target[name], copy = options[name];

        if (target === copy) continue;

        if (deep && copy && typeof copy === 'object' && !copy.nodeType) {
          target[name] = extend(deep, src || (copy.length != null ? [] : {}), copy);
        } else if (copy !== undefined) {
          target[name] = copy;
        }
      }
    }
  }

  return target;
}

выдергнул с ВК