Is web delivery for Node.js apps a thing?
I'm not aware of a project that provides that out of the box. For local development, it is common to have hot reload. If something at the file level changes, it restarts the server. That is somewhat related, as you could trigger the updates on the file system remotely. Installing libraries could also be simulated by directly updating the  node_modules folder.

Beside that NodeJs itself provides ways to run arbitrary code without process restarts. One way is to use eval (as part of JavaScript). The other is to reload a file. Normally, require caches the file after it executed it, but you can purge this cache (require.cache), and require the file again. That is what the decache library does.

In theory, NodeJs provides all the tools to allow remote code being applied. Of course, from a security perspective, you open yourself to all kind of attacks. Make sure requests come from a trusted source.


  But for web-delivery, I think a workflow for deploying a node.js-centric application and keeping it up to date would use some other mechanism. What is that mechanism? If docker is the way, then maybe I just need to refocus my question to find out how to auto-update docker containers


I would also see it less as a matter of updating a NodeJs application (driven by the application itself), but rather as  of a good deployment pipeline (driven from outside). In the end, deployment is nothing else than pushing changes to production.

There are a variety of deployment approaches for NodeJs applications:


Classic deployment on a server
Docker based deployments (e.g., Kubernetes)
Serverless (e.g., AWS Lambda, Serverless Framework)
Platform as a service (e.g., Heroku)


If you are not sure, the easiest to get started with are serverless deployments (supported on all major providers: AWS Lambdas, Google Cloud Functions, Azure Functions), or platform as a service solutions (e.g., Heroku). Kubernetes (as a popular framework for deploying Docker containers) is powerful, but has a steep learning curve.