<nav class="navbar navbar-expand-sm bg-light navbar-light justify-content-center mb-3">
    <ul class="navbar-nav">
        <li class="nav-item">
            <!-- event handler nie widzi tego tagu, rzuca nulla -->
            <a class="nav-link" href='#' id="articleBtn">Show last 5 articles</a>
        </li>
    </ul>
</nav>