After installing the drop-down menu in the navigation menu, the page top button JS that worked so far has stopped working.

The drop-down works, but the page top button doesn't work

<script src = "https://code.jquery.com/jquery-1.12.4.min.js" integrity = "sha256-ZosEbRLbNQzLpnKIkEdrPv7lOy9C27hHQ + Xp8a4MxAQ =" crossorigin = "anonymous"></script >
    <script src = "https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js" integrity = "sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQn4" F86dIHz0 = " script>
    <script src = "https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity = "sha384-q8i/X + 965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH + 8abtTE1Pi6jizo" crossorigin = "anonymous"></>
    <script src = "https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity = "sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM + B07jRM" crossorigin = ""
    <script type = "text/javascript" src = "js/slick.min.js"></script>
    <script type = "text/javascript" src = "js/script.js"></script>
</body>
</html>

In the following order, the page top button will move and the drop down will not work.

<script src = "https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity = "sha384-q8i/X + 965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH + 8abtTE1Pi6jizo" crossoriginanony "></script>
<script src = "https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity = "sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM + B07jRM" crossorigin = ""
<script type = "text/javascript" src = "js/slick.min.js"></script>
<script type = "text/javascript" src = "js/script.js"></script>
<script src = "https://code.jquery.com/jquery-1.12.4.min.js" integrity = "sha256-ZosEbRLbNQzLpnKIkEdrPv7lOy9C27hHQ + Xp8a4MxAQ =" crossorigin = "anonymous"></script>
<script src = "https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js" integrity = "sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQn4" F86dIHz0 = " script>
</body>
</html>

Excerpt from script.js

// Smooth scroll
$(function () {
    $('a [href ^ = "#"]'). click (function () {
        var speed = 500;
        var href = $(this) .attr ("href");
        var target = $(href == "#" || href == ""? 'html': href);
        var position = target.offset (). top;
        $("html, body"). animate ({scrollTop: position}, speed, "swing");
        return false;
    });
});

// Page top button
$(function () {
    var topBtn = $('# page_top');
    topBtn.hide ();
    // Button display when scroll reaches 100
    $(window) .scroll (function () {
        if ($(this) .scrollTop ()>500) {
            topBtn.fadeIn ();
        } else {
            topBtn.fadeOut ();
        }
    });
    // Scroll to top
    topBtn.click (function () {
        $('body, html'). animate ({
            scrollTop: 0
        }, 500);
        return false;
    });
});

If jquery-1.12.4.min.js and popper.min.js required for the drop-down menu are listed above, only the page top button JS in the script.js below will not function.

Please note that we will add any additional information if necessary.