Test
<div class="sampleshop-bar">
    <p class="shop-btn" data-sample-cart="">
        <a href="javascript:void(0);" title="Sample(s) aanvragen" data-sample-cart-btn >
            <span class="shop-btn__text">
                Sample(s) aanvragen            </span>

            <span class="shop-btn__icon">
                <i class="icon icon--cart"></i>
                <span class="shop-btn__count">
                    <span data-sample-count>0</span>
                    /5                </span>
            </span>
        </a>
    </p>
</div>

<dialog class="dialog" data-sample-cart-popup>
    <button type="button" class="btn-close" aria-label="Close" data-sample-cart-close></button>
    <iframe src="sample-aanvragen?show_header=0&amp;show_footer=0" frameborder="0" width="1200" height="700"></iframe>
</dialog>
test