Print the document, for debugging

debug.js

function printDocument(node, startIndex = 0) {
	let skip, tmp;

	let depth = 0;
	let index = startIndex;

	let items = [];

	function add(node) {
		let str = index + "-" + node.nodeName;
		items.push(str);
	}

	// Always start with the initial element.
	do {
		if ( !skip && (tmp = node.firstChild) ) {
			depth++;
			add(tmp);
			index++;
		} else if ( tmp = node.nextSibling ) {
			skip = false;
			add(tmp);
			index++;
		} else {
			// Skipped or no first child and no next sibling, so traverse upwards,
			tmp = node.parentNode;
			// and decrement the depth.
			depth--;
			// Enable skipping, so that in the next loop iteration, the children of
			// the now-current node (parent node) aren't processed again.
			skip = true;
		}

		// Instead of setting node explicitly in each conditional block, use the
		// tmp var and set it here.
		node = tmp;

		// Stop if depth comes back to 0 (or goes below zero, in conditions where
		// the passed node has neither children nore next siblings).
	} while ( depth > 0 );

	console.log(items.join("|"));
}