Javascript file is not called after loading content using jquery

Question

I would like to load the content inside the modal, it works well, but after loading the content the javascript file is not displayed. This is my code:

index.html.twig ,                      

This is the ajax_backend.js function for loading content:

$(document).on('show.bs.modal', "#myModal", function (e) {
    // load content inside modal from the link
    var link = $(e.relatedTarget);
    showLoadingDiv();

    $(this).load(link.attr("href"), function (responseTxt, statusTxt, xhr) {
        if (statusTxt == "success") {
            collectionInsideModal();
            hideLoadingDiv();
        }
        if (statusTxt == "error")
            alert("Erreur: " + xhr.status + ": " + xhr.statusText);
        hideLoadingDiv();
    });

    $(this).on("hidden.bs.modal", function () {
        $(this).html('');
    });
});

after loading the contents, the nifty.min.js file is not displayed, so I have to reload this file as follows:

 <div>
 // content that will be loaded
 </div>
 <script src="{{ asset('backend/js/nifty.min.js') }}"></script>

How to fix it, so that every time you reload the JS file with the content?

This file nifty.min.js is not specified