code: function cloneVNode (vnode) {
    const cloned = new VNode(
      vnode.tag,
      vnode.data,
      // #7975
      // clone children array to avoid mutating original in case of cloning
      // a child.
      vnode.children && vnode.children.slice(),
      vnode.text,
      vnode.elm,
      vnode.context,
      vnode.componentOptions,
      vnode.asyncFactory
    );
    cloned.ns = vnode.ns;
    cloned.isStatic = vnode.isStatic;
    cloned.key = vnode.key;
    cloned.isComment = vnode.isComment;
    cloned.fnContext = vnode.fnContext;
    cloned.fnOptions = vnode.fnOptions;
    cloned.fnScopeId = vnode.fnScopeId;
    cloned.asyncMeta = vnode.asyncMeta;
    cloned.isCloned = true;
    return cloned
  }
docs: optimized shallow clone used for static nodes and slot nodes because they may be reused across multiple renders, cloning them avoids errors when DOM manipulations rely on their elm reference.