class NavigationStart extends RouterEvent {  constructor(id: number, url: string, navigationTrigger?: NavigationTrigger, restoredState?: { [k: string]: any; navigationId: number; } | null): NavigationStart;  readonly type: EventType.NavigationStart;  navigationTrigger?: NavigationTrigger | undefined;  restoredState?: { [k: string]: any; navigationId: number; } | null | undefined;  override id: number;  override url: string;}
    
    

Identifies the call or event that triggered the navigation. An imperative trigger is a call to router.navigateByUrl() or router.navigate().

The navigation state that was previously supplied to the pushState call, when the navigation is triggered by a popstate event. Otherwise null.

The state object is defined by NavigationExtras, and contains any developer-defined state value, as well as a unique ID that the router assigns to every router transition/navigation.

From the perspective of the router, the router never "goes back". When the user clicks on the back button in the browser, a new navigation ID is created.

Use the ID in this previous-state object to differentiate between a newly created state and one returned to by a popstate event, so that you can restore some remembered state, such as scroll position.

A unique ID that the router assigns to every router navigation.

The URL that is the destination for this navigation.