angular 6 queryParamsHandling difference between merge and perserve

Question

In angular, What is the the difference between

queryParamsHandling:"merge" and queryParamsHandling:"preserve"?

Answer 1

If you change the route from one url to another say from /firstUrl?name=bat7 to /secondUrl that time you need to say

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

so that the queryParam "name" will not be lost

http://localhost:4200/secondUrl?name=bat7

and if you say merge like,

this.router.navigate(['/secondUrl/newVal'], { queryParams: { age: 'not-known'}, queryParamsHandling: 'merge' });

it would be like below

http://localhost:4200/secondUrl?name=bat7&age=not-known

The same query parameter can be taken to different routes and merged with needed params.