DFS.html

<root>
    root
    <a>
        a
        <aa>aa</aa>
        <bb>bb</bb>
    </a>
    <b>b
        <ba>ba</ba>
        <bb>bb</bb>
    </b>
</root>

<script>
function DFS(rootNode) {
    const next = [rootNode]

    while (next.length) {
        const node = next.pop()

        if (node.nodeName === '#text') { continue }

        console.log(node)

        const { childNodes } = node

        for (let i = childNodes.length - 1; i >= 0; --i) {
            next.push(childNodes[i])
        }
    }
}

DFS(document.querySelector('root'))
</script>