Bookmarklet: Show HTML tags occurrences

bookmarklet.js

/**
 * A bookmarklet, which displays the number of occurrences of each HTML tag in the DOM
 * 
 * @author ComFreek
 * @license MIT
 * @link http://softwarerecs.stackexchange.com/a/10329/583
 */


function getTagCounts() {
	var treeWalker = document.createTreeWalker(document.documentElement, NodeFilter.SHOW_ELEMENT);

	var tagCounts = {};
	while (treeWalker.nextNode()) {
		var node = treeWalker.currentNode;
		if (!(node.tagName in tagCounts)) {
			tagCounts[node.tagName] = 0;
		}
		tagCounts[node.tagName]++;
	}
	return tagCounts;
}

function convToArray(tagCounts) {
	// to array
	var tags = [];

	for (var tagName in tagCounts) {
		if (tagCounts.hasOwnProperty(tagName)) {
			tags.push({tagName: tagName, count:	 tagCounts[tagName]});
		}
	}
	return tags;
}

function sortCompareFn(tagA, tagB) {
	if (tagA.count > tagB.count) {
		return -1;
	}
	else if (tagA.count < tagB.count) {
		return 1;
	}
	else {
		return 0;
	}
}

function arrayToSimpleStr(tags) {
	// output
	var str = "";
	for (var i=0; i<tags.length; i++) {
		str += tags[i].tagName;
		str += ": ";
		str += tags[i].count;
		str += "\n";
	}
	return str;
}

var sortedTagCounts = convToArray(getTagCounts()).sort(sortCompareFn);
alert(arrayToSimpleStr(sortedTagCounts));

Bookmarklet: Show HTML tags occurrences

Bookmarklet: Show HTML tags occurrences

Tested with:
- Google Chrome
- Mozilla Firefox

Does not work with (yet): IE 11

License: MIT
Author: ComFreek
Written for: http://softwarerecs.stackexchange.com/questions/10290/html-element-statistics-of-the-current-page

Very nice :) Thanks for your work, ComFreek! As far as I tested, it works great.

Just in case you’d like to improve it: I think it would be useful to sort the elements alphabetically, when they have the same count. (I used this sort in the example in my question, but didn’t specify it as requirement, as it’s just nice to have but not required.)