JSFiddle - React, Tailwind, and code Playground

HTML

<body>
<nav>
    <ul>
        <li><a id="homeContainer" href="home.html">Home</a></li>
        <li><a id="theorieContainer" href='test.html'>test</a></li>
        <li><a id="praktijkContainer" href="test2.html">test2</a></li>
        <li><a id="contactContainer" href="contact.html">Contact</a></li>
    </ul>
</nav>
  <div id='container'>
     standard textttt
  </div> 

</body>

JavaScript

<script type="text/javascript">        
        $(document).ready(function()
        {
            $( 'li>a[id$="Container"]' ).click(function(event)
            {
                event.preventDefault();
                var href = $(this).attr('href');
                $('#container').load(href);
                return false;
            });
        });
    </script>
    
    <script>
        
        $(function(){
            $('#contact').validate({
            submitHandler: function(form) {
                    $(form).ajaxSubmit({
                    url: 'process.php',
                    success: function() {
                        $('#contact').hide();
                        $('#contact-form').append("<p class='thanks'>thanks test.</p>")
                        }
                    });
                }
            });         
        });
    </script>
    
    <script>
    if (!Modernizr.input.placeholder){
         $('input[placeholder], textarea[placeholder]').placeholder();
        }
    </script>