<pre class="shiki github-dark shaku"><code>/** * @param {HTMLElement} tree * @return {string[]} */function getTags(tree) { let res = new Set(); const traverse = (node) =&gt; { if (!node) return; res.add(node.tagName.toLowerCase()); for (const child of node.children) traverse(child); } traverse(tree); return [...res];}</code></pre>

Simple

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.…