
Previously, the `ngOnDestroy` method called `unsubscribe` regardless of if `subscription` had been initialized. This can lead to an error attempting to call `unsubscribe` of undefined. This change prevents this error, and instead only attempts `unsubscribe` when the subscription has been defined. PR Close #38344
Angular Router
Managing state transitions is one of the hardest parts of building applications. This is especially true on the web, where you also need to ensure that the state is reflected in the URL. In addition, we often want to split applications into multiple bundles and load them on demand. Doing this transparently isn’t trivial.
The Angular router is designed to solve these problems. Using the router, you can declaratively specify application state, manage state transitions while taking care of the URL, and load components on demand.
Guide
Read the dev guide here.