See https://coding-and-design.blogspot.de/2016/11/are-all-element-tags-closed-testing-it.html for more info

closed-tag-testing.js

// See https://coding-and-design.blogspot.de/2016/11/are-all-element-tags-closed-testing-it.html for more info
var 凸 = typeof global === 'undefined' ? 凸 : global.tmp;
var 凸 = (function (凸) {
	凸.buildGetPageFunction = function buildGetPageFunction() {
		if (typeof global === 'undefined') {
			// Browser
			return function (url, callback) {
				var xhr = new XMLHttpRequest();
				xhr.onreadystatechange = function () {
					if (xhr.readyState === XMLHttpRequest.DONE) {
						return callback(xhr.responseText);
					}
				};
				xhr.open('GET', url, true);
				xhr.send(null);
			};
		} else {
			// Node
			return function (url, callback) {
				var request = require("request");
				request({ url: url }, function (err, response, responseText) {
					if (!err && response.statusCode === 200) {
						return callback(responseText);
					} else {
						throw err;
					}
				});
			};
		}
	};
	return 凸;
}(凸 || {}));


var 凸 = (function (凸) {
	function isSelfClosingTag(tagName) {
		return tagName.match(/area|base|br|col|embed|hr|img|input|keygen|link|menuitem|meta|param|source|track|wbr|script/i);
	}

	function displayLine(line, array) {
		return ('Line #' + line + ': ' + array[line - 1]);
	}
	凸.checkHtml = function checkHtml(p) {
		// Based on http://jona.ca/blog/unclosed-tag-finder
		var
			array1 = p.constructor === Array ? p : p.split('\n'),
			tags = [],
			tag,
			openTags = [],
			openTag,
			i,
			j,
			line,
			array2,
			matches,
			closingTag;
		for (i = 0; i < array1.length; i++) {
			line = array1[i];
			array2 = line.match(/<[^>]*[^/]>/g) || [];
			for (j = 0; j < array2.length; j++) {
				tag = array2[j];
				matches = tag.match(/<\/?([a-z0-9]+)/i);
				if (matches) {
					tags.push({ tag: tag, name: matches[1], line: i + 1, closing: tag[1] === '/' });
				}
			}
		}
		if (tags.length === 0) {
			return 'No tags found.';
		}
		for (i = 0; i < tags.length; i++) {
			tag = tags[i];
			if (tag.closing) {
				closingTag = tag;
				if (isSelfClosingTag(closingTag.name)) {
					continue;
				}
				if (openTags.length === 0) {
					return [
						'Closing tag ' + closingTag.tag + ' on line ' + closingTag.line + ' does not have corresponding open tag.',
						displayLine(closingTag.line, array1),
					].join('\n');
				}
				openTag = openTags[openTags.length - 1];
				if (closingTag.name !== openTag.name) {
					return [
						'Closing tag ' + closingTag.tag + ' on line ' + closingTag.line + ' does not match open tag ' + openTag.tag + ' on line ' + openTag.line + '.',
						displayLine(openTag.line, array1),
						displayLine(closingTag.line, array1)
					].join('\n');
				} else {
					openTags.pop();
				}
			} else {
				openTag = tag;
				if (isSelfClosingTag(openTag.name)) {
					continue;
				}
				openTags.push(openTag);
			}
		}
		if (openTags.length > 0) {
			openTag = openTags[openTags.length - 1];
			return [
				'Open tag ' + openTag.tag + ' on line ' + openTag.line + ' does not have a corresponding closing tag.',
				displayLine(openTag.line, array1),
			].join('\n');
		}
		return 'Success: No unclosed tags found.';
	};
	return 凸;
}(凸 || {}));

(function () {
	var url = (typeof global === 'undefined') ? document.location.href : "http://example.com";
	凸.buildGetPageFunction()(url, function (page) {
		console.log("### Checking " + url + "\n\n" + 凸.checkHtml(page) + "\n\n");
	});
	console.log("### Checking <div>\n\n" + 凸.checkHtml("<div>") + "\n\n");
	console.log("### Checking ['<div>']\n\n" + 凸.checkHtml(["<div>"]) + "\n\n");
})();