So I am trying to put a Javascript variable in a twig form. This is where I declare my Javascript variable :

<script>
    function add() {
        var active_date = $('#calendar').evoCalendar('getActiveDate');
        sessionStorage.setItem("myDate", active_date);
     
    }
</script>


    <div class="contact-form">
        <a  href="{{ path('rdv_new') }}" class="btn btn-3" onclick="add()" > Book now! </a>

    </div>

And in another file .html.twig I am calling this variable but I can't find a way to assign it to my twig form like so

 <script>
     var myDate = sessionStorage.getItem("myDate");
     
   
 </script>

   {{ form_widget(form.date, {'value' : myDate}) }}