<script src="https://pay.sandbox.datatrans.com/upp/payment/js/datatrans-2.0.0.min.js"></script>
<form id="paymentForm"
      data-merchant-id="1100004624"
      data-amount="1000"
      data-currency="CHF"
      data-refno="123456789"
      data-sign="30916165706580013">
    <a id="paymentButton" class="btn btn-primary">Pay CHF 10.00</a>
</form>

<script type="text/javascript">
    $("#paymentButton").click(function () {
        Datatrans.startPayment({'form': '#paymentForm'});
    });
</script>