Custom error handler

Every navigation will either succeed, will be cancelled, or will error. There are two ways to observe this.

The router.events observable will emit:

• NavigationStart when navigation stars
• NavigationEnd when navigation succeeds
• NavigationCancel when navigation is canceled
• NavigationError when navigation fails

All of them contain the id property we can use to group the events associated with a particular navigation.

If we call router.navigate or router.navigateByUrl directly, we will get a promise that:

• will be resolved with true if the navigation succeeds
• will be resolved with false if the navigation gets cancelled
• will be rejected if the navigation fails

Navigation fails when the router cannot match the URL or an exception is thrown during the navigation. Usually this indicates a bug in the application, so failing is the right strategy, but not always. We can provide a custom error handler to recover from certain errors as shown in the following code:

function treatCertainErrorsAsCancelations...