In angular 2 how to preserve query params and add additional query params to route

In Angular 4+, preserveQueryParams has been deprecated in favor of queryParamsHandling. The options are either 'merge' or 'preserve'.

In-code example (used in NavigationExtras):

this.router.navigate(['somewhere'], { queryParamsHandling: "preserve" });

In-template example:

<a [routerLink]="['somewhere']" queryParamsHandling="merge">