code: function clone(target) {
    if (target == null || typeof target !== "object") return target;
    var cloned = target.constructor ? target.constructor() : Object.create(null);
    for (var attr in target) {
      if (target.hasOwnProperty(attr)) {
        cloned[attr] = target[attr];
      }
    }
    return cloned;
  }
docs: Don't need the full-out "clone" mechanism here, since if you're trying to set things other than empty arrays/objects on your sub-classed `Error` object, you're probably doing it wrong.