This won't show anything visually. You need to use JavaScript APIs to show / hide it.
<pure-dialog id="example" data-title="Pure Dialog Demo" buttons="Absolutely, No, Maybe"> Is this project worth a star? </pure-dialog>
<button onclick="document.querySelector('#example').show()">show</button>
<button onclick="document.querySelector('#example').showModal()">showModal</button>
<script> // listen for button clicks in any dialog! document.addEventListener('pure-dialog-button-clicked', function(e) { alert(e.detail + ' clicked!'); }); </script>