It starts /projects/ npm start and then after deployment you can make a volume like this
docker run -v /local-project:/project .... that will replace this /project folder and if you have server.js * doing all the web work you are good to go, you can now make changes in your host and supervisor will auto restart your web server for development. This works well with vagrant, docker toolbox needs to be improved at the time of this writing.
This is designed to work perfectly with a Vagrant VM for local development using Linux on say a mac or PC. See the bitbucket repository to see the source code.
Just make sure your package.json has something like this
"start": "supervisor server.js"
You can see source code here https://github.com/zuz9/node-folder-watch-vagrant-docker