route only when coming from parent route code example

Example: how-do-i-navigate-to-a-parent-route-from-a-child-route

// via router link
// The RouterLink directive always treats the provided link as a delta to the current URL:

[routerLink]="['/absolute']"
[routerLink]="['../../parent']"
[routerLink]="['../sibling']"
[routerLink]="['./child']"     // or
[routerLink]="['child']" 

// with route param     ../../parent;abc=xyz
[routerLink]="['../../parent', {abc: 'xyz'}]"
// with query param and fragment   ../../parent?p1=value1&p2=v2#frag
[routerLink]="['../../parent']" [queryParams]="{p1: 'value', p2: 'v2'}" fragment="frag"


// via router
// The navigate() method requires a starting point (i.e., the relativeTo parameter). If none is provided, the navigation is absolute:
...
constructor(private router: Router, private route: ActivatedRoute) {}
...
this.router.navigate(["/absolute/path"]);
this.router.navigate(["../../parent"], {relativeTo: this.route});
this.router.navigate(["../sibling"],   {relativeTo: this.route});
this.router.navigate(["./child"],      {relativeTo: this.route}); // or
this.router.navigate(["child"],        {relativeTo: this.route});

// with route param     ../../parent;abc=xyz
this.router.navigate(["../../parent", {abc: 'xyz'}], {relativeTo: this.route});
// with query param and fragment   ../../parent?p1=value1&p2=v2#frag
this.router.navigate(["../../parent"], {relativeTo: this.route, 
    queryParams: {p1: 'value', p2: 'v2'}, fragment: 'frag'});

// navigate without updating the URL 
this.router.navigate(["../../parent"], {relativeTo: this.route, skipLocationChange: true});