I roughly sorted out two ideas and ways of understanding based on what was said online.
The first understanding: 
The second understanding:
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I forgot to post the code in the previous question, now I’m attaching the specific code https://github.com/ghcrainy/designpatterns
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
