https://www.cnblogs.com/libin-1/p/6845669.html Reference
The bottom layer of the vue virtual DOM uses the DomcumentFragment api to create a memory pool first, put the real dom into the memory pool, then uniformly modify the node, and then put the node back into the real dom through the appendchild() method
For details, please refer to my github project https://github.com/woshiitdaniu/Simple-Vue/tree/add-observer/js
If you need to get the specific execution process, please make adjustments by yourself^_^