<html>
<body>
<div>some text</div>
<div id="has-open"></div>
<div id="has-closed"></div>
<div id="has-other"></div>
<script>
(function makeShadowDOM() {
document
.getElementById("has-open")
.attachShadow({ mode: 'open' });
document
.getElementById("has-closed")
.attachShadow({ mode: 'closed' });
// has-other shadow dom should not get created,
// so parsing the html tag should still succeed
document
.getElementById("has-other")
.attachShadow({ mode: 'nonsense-mode-does-not-exist' });
})()
</script>
</body>
</html>