code: function(obj, visitor, context) {
        var result;
        this.preorder(obj, function(value, key, parent) {
          if (visitor.call(context, value, key, parent)) {
            result = value;
            return stopWalk;
          }
        }, context);
        return result;
      }
docs: Performs a preorder traversal of `obj` and returns the first value which passes a truth test.