Inform users of your package of updates in a non-intrusive way.Whenever you initiate the update notifier and it's not within the interval threshold, it will asynchronously check with npm in the background for available updates, then persist the result. The next time the notifier is initiated, the result will be loaded into the .update property. This prevents any impact on your package startup performance. The update check is done in a unref'ed child process. This means that if you call process.exit, the check will still be performed in its own process.