docs: function cloneEvents(origin, clone, deep) {
        var listeners = origin._listeners
        if (listeners) {
          clone._listeners = listeners
          for (var type in listeners) {
            clone.addEventListener(type, listeners[type])
          }
        }
        if (deep && origin.children && origin.children.length) {
          for (var i = 0, l = origin.children.length; i < l; i++) {
            cloneEvents(origin.children[i], clone.children[i], deep)
          }
        }
      }