I am a novice. I have just come into contact with the node.js and express frameworks. I have configured routing according to the online tutorial, but there are some problems, as follows:

first of all, the file structure is as follows:

index.js:

 

 try to solve it by yourself. If the  routes/index.js  and  routes/about.js  files are written into the  index.js  file (without module export), then the  about  page can respond normally, but not in different modules. 
 I have just come into contact with this aspect, and I don"t quite understand what the problem is. I hope I can have some guidance from my predecessors. Thank you.