NextJS - Appending a query param to a dynamic route

Question

In my NextJS app, I have a language selector that's visible on every page. When I select a new language, I just want to replace the current URL by appending a query param lang=en to it.

Here's the function that replaces the URL:

const changeLanguage = (lang: LanguageID) => {
    replace({
      pathname,
      query: { ...query, lang },
    });
  };

In this example, replace, query and pathname are coming from the next router.

Now, everything works for static routes, but I'm unable to make it work for dynamic routes. For example, I have the following folder structure:

pages
|_customers
|__index.tsx
|__[customerId].tsx

If I'm on http://localhost/customers and I change my language to English, the URL changes to http://localhost/customers?lang=en which is what I want. However, if I'm on http://localhost/customer/1 and I change my language to English, the URL changes to http://localhost/customers/[customerId]?customerId=1&lang=en, instead of the URL I'm expecting http://localhost/customers/1?lang=en.

Now, I know that I could use asPath on the router, and reconstruct the query string object by appending lang to it, but I feel that it's something that should be build into Next. Also, I know it could be easily done with vanilla JS, but it's not the point here.

Am I missing something? Is there an easier way to append query params to a dynamic route without doing a server-side re-rendering?

Thanks

Answer 1

Just add more param to current router then push itself

const router = useRouter();
router.query.NEWPARAMS = "VALUE"
router.push(router)