HTML normalization to allow for consistent comparison of HTML

normalize_html.js

/**
* Order HTML attributes for consistent HTML comparison.
*
* Adapted from google-code-prettify
* http://code.google.com/p/google-code-prettify/source/browse/trunk/src/prettify.js#311
* Apache license, Copyright (C) 2006 Google Inc.
*/
function normalizeHtml(node) {
	var html = '';
	switch (node.nodeType) {
		case 1:  // an element
			var name = node.tagName.toLowerCase();

			html += '<'+name;
			var attrs = node.attributes;
			var n = attrs.length;
			if (n) {
				var sortedAttrs = [];
				for (var i = n; --i >= 0;) { sortedAttrs[i] = attrs[i]; }
				sortedAttrs.sort(function (a, b) {
					return (a.name < b.name) ? -1 : a.name === b.name ? 0 : 1;
				});
				attrs = sortedAttrs;

				for (var i = 0; i < n; ++i) {
					var attr = attrs[i];
					if (!attr.specified) { continue; }
					html += ' ' + attr.name.toLowerCase() +
						'="' + attribToHtml(attr.value) + '"';
				}
			}
			html += '>';
			for (var child = node.firstChild; child; child = child.nextSibling) {
				html += normalizeHtml(child);
			}
			if (node.firstChild || !/^(?:br|link|img)$/.test(name)) {
				html += '<\/' + name + '>';
			}
			break;
		case 3: case 4: // text
			html += textToHtml(node.nodeValue);
			break;
	}

	return html;
}

function attribToHtml(str) {
	return str.replace(pr_amp, '&amp;')
		.replace(pr_lt, '&lt;')
		.replace(pr_gt, '&gt;')
		.replace(pr_quot, '&quot;');
}

var pr_amp = /&/g;
var pr_lt = /</g;
var pr_gt = />/g;
var pr_quot = /\"/g;
/**
* Escape html special characters.
*/
function textToHtml(str) {
	return str.replace(pr_amp, '&amp;')
		.replace(pr_lt, '&lt;')
        .replace(pr_gt, '&gt;');
}