Firebase query() with condition ( Version 9 web )

Question

  let q = query(
            collection(dbFirebase, "users"),
            where("uid", "!=", id),
            orderBy("uid"),
            limit(1)
        )
        if (lastVisible) {
            q = q.startAfter(lastVisible)
        }

I just want to add condition for the query 'startAfter' if i don't have value ( lastVisible ).

If i don't have value (lastVisible), my request is good.

If i have a value (lastVisible), I have an error.

My error : Error TypeError: q.startAfter is not a function

Thanks for help.