What you are looking for is a good JavaScript documentation generator. I found a decent one here http://apidocjs.com/example/.
This will allow you to use just Express as OP asked.
Swagger isn’t for generating docs, it’s for making APIs. So you are going to need to learn a full system to get that feature.
I found a couple more here that I haven’t fully looked into yet which seem promising:
Docco here JSDoc here and an article on Documentor for Node