Using Swup - reloading javascript on every file

Question

I'm using PHP with Swup to refresh pages without refresh the whole site. I'm using JavaScript function on every page (inside the body tag for exa) with functions that using ajax reguests every x seconds. code example:

<script defer>
    $(document).ready(function () {
    $.ajax({....});
// along with some more functions for handling the ajax request.
</script>

I got a main js file that handles the const swup = new Swup(); code. my question is, how i can handle it, so it will load the js tag on the body of each page, and when i change the page, it will unload the previous requests/js (if needed?) and wont refresh the global js (it doesnt atm)

thanks.