Using Next.js and Typescript

Hi everyone, I was struggling to get the the first indicators looking active when selecting a page in Mozilla Firefox. In Chromium everything works fine. I made it work by using a querrySelector to get the first element and switch its aria-selected-attribute to "true". So I hadn't to write If-Clauses in the map-Functions, which render the Indicator-elements. Is there a better or easier practice to acquire this effect?