When called, requests that the Node.js event loop not exit so long as the fs.StatWatcher is active. Calling watcher.ref() multiple times will have no effect.

By default, all fs.StatWatcher objects are "ref'ed", making it normally unnecessary to call watcher.ref() unless watcher.unref() had been called previously.

When called, the active fs.StatWatcher object will not require the Node.js event loop to remain active. If there is no other activity keeping the event loop running, the process may exit before the fs.StatWatcher object's callback is invoked. Calling watcher.unref() multiple times will have no effect.