Reload-on-change is a relatively common feature. While a lot of modern web programming frameworks and libraries don't rely heavily on in-memory state, this is very much a different experience from having your editor constantly communicating with a live process.
There's a package for the nodejs ecosystem called "nodemon" https://github.com/remy/nodemon
That restarts the webserver on filechanges automatically.
The former is very basic and I don't really use it, but nodemon is quite nifty.