Step 3:

regex-html-3.js

// Parse an open tag
const success = pull(/^<([a-zA-Z][a-zA-Z0-9\-]*)>/, tag => {
	const new_tag = { tag, attributes: {}, children: [] };
	cursor.children.push(new_tag);
	parse_content(new_tag);
}) ||
// Parse close tag
pull(/^<\/([a-zA-Z][a-zA-Z0-9\-]*)>/, tag => {
	if (cursor.tag.toLowerCase() !== tag.toLowerCase()) {
		throw new Error("Unmatched close tag");
	}
	run = false;
})
// Parse a text node
|| pull(/^([^<]+)/, text => {
	cursor.children.push({
		text
	});
});