JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://www.contentu.be/crm/new/aanpas-modal.php"></script>
<a href="javascript:;" data-id="1" onclick="showAjaxModal();" class="btn btn-primary btn-single btn-sm">Show Me</a>

<div class="modal fade" id="modal-7">
    <div class="modal-dialog">
        <div class="modal-content">

            <div class="modal-header">
                <button type="button" class="close" data-dismiss="modal" aria-hidden="true">&times;</button>
                <h4 class="modal-title">Dynamic Content</h4>
            </div>

            <div class="modal-body">

                Content is loading...

            </div>

            <div class="modal-footer">
                <button type="button" class="btn btn-white" data-dismiss="modal">Close</button>
                <button type="button" class="btn btn-info">Save changes</button>
            </div>
        </div>
    </div>
</div>

JavaScript

function showAjaxModal()
    {
        var uid = $(this).data('id');
        var url = "aanpas-modal.php?id=" + uid;
        jQuery('#modal-7').modal('show', {backdrop: 'static'});
        jQuery('#modal-7 .modal-body').load(url);

    }