<pre class="shiki github-dark shaku"><code>/** * @param {HTMLElement} tree * @return {string[]} */function getTags(tree) { const tags = new Set(); const treeWalker = document.createTreeWalker(tree, NodeFilter.SHOW_ELEMENT); let node = treeWalker.currentNode; tags.add(node.tagName); while (node = treeWalker.nextNode()) { tags.add(node.tagName); } return [...tags].map(tag =&gt; tag.toLowerCase());}</code></pre>

Using a TreeWalker

Given a DOM tree, please return all the tag names it has. Your function should return a unique array of tags names in lowercase, order doesn't matter.…