App Closed / App Killed Event

We have an Hosted web app, we want to monitor the app crashes that could have happened because of insufficient memory.
Is there any way to figure this out? any event which we can listen to?
Also, can we listen to app close event?

There is no event for app termination. (See App Lifecycle.) To monitor memory usage, you can use the CLI, Beanviser, or Web Inspector. We recommend less than 250MB. Thank you.