TIP

This script passes all the tests in the autodiscovery test suite, available at http://diveintomark.org/tests/client/autodiscovery/.

Save the following user script as feedcollector.user.js:

	// ==UserScript==
	// @name		   Feed Collector
	// @namespace	   http://diveintomark.org/projects/greasemonkey/
	// @description  collect auto-discovered feeds in visited pages
	// @include	   http://*
	// ==/UserScript==

	function getPageFeeds() {
		var dateNow = new Date();
		var elmPossible = document.evaluate("//*[@rel][@type][@href]",
			document, null, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null);
		var arFeeds = new Array();
		for (var i = 0; i < elmPossible.snapshotLength; i++) {
			var elm = elmPossible.snapshotItem(i);
			if (!elm.rel) { continue; }
			if (!elm.type) { continue; }
			if (!elm.href) { continue; }

			var sNodeName = elm.nodeName.toLowerCase();
			if ((sNodeName != 'link') && (sNodeName != 'a')) { continue; }
			var sRel = elm.rel.toLowerCase();
			var bRelIsAlternate = false;
			var arRelValues = sRel.split(/\s/);
			for (var j = arRelValues.length - 1; j >= 0; j--) {

				bRelIsAlternate = bRelIsAlternate ||
				(arRelValues[j] == 'alternate');
			}
			if (!bRelIsAlternate) { continue; }
			var sType = elm.type.toLowerCase().trim();
			if ((sType != 'application/rss+xml') &&
				(sType != 'application/atom+xml') &&
				(sType != 'text/xml')) { continue; }
			var urlFeed = elm.href.trim();
			var sTitle = elm.title.trim() || '';
			arFeeds.push({href: urlFeed,
				  title: sTitle,
				  type: sType,
				  homepage: location.href});
		}
		return arFeeds;
	}

	function getHistoryCount() {
		return GM_getValue('count', 0);
	}

	function getHistoryItem(iHistoryIndex) {
		var urlFeed = GM_getValue(iHistoryIndex + '.href', '');
		if (!urlFeed) { return null; }
		var sTitle = GM_getValue(iHistoryIndex + '.title', '');
		var sType = GM_getValue(iHistoryIndex + '.type', '');
		var sHomepage = GM_getValue(iHistoryIndex + '.homepage', '');
		return {href: urlFeed,
				title: sTitle,
				type: sType,
				homepage: sHomepage};
		}

		function getAllHistoryItems() {
			var iHistoryCount = getHistoryCount();
			var arFeeds = new Array();
			for (var i = 0; i < iHistoryCount; i++) {
				arFeeds.push(getHistoryItem(i));
			}
			return arFeeds;
		}

		function findHistoryItemByURL(urlFeed) {
			var iHistoryCount = getHistoryCount();
			for (var i = 0; i < iHistoryCount; i++) {
				var oHistory = getHistoryItem(i);

			if (oHistory.href == urlFeed) {
				return i;
			}
		}
		return -1;
	}

	function addToHistory(oFeedInfo) {
		var iHistoryCount = getHistoryCount();
		if (findHistoryItemByURL(oFeedInfo.href) != -1) { return; }
		if (document.title && oFeedInfo.title) {
			sFeedTitle = document.title + ' - ' + oFeedInfo.title;
		} else if (document.title) {
			sFeedTitle = document.title;
		} else if (oFeedInfo.title) {
			sFeedTitle = oFeedInfo.title;
		} else {
			sFeedTitle = oFeedInfo.href;
		}
		sFeedTitle = sFeedTitle.replace(/\s+/g, ' ');
		sFeedTitle = sFeedTitle.replace(/[^A-Za-z0-9\- ]/g, '');
		var sType = oFeedInfo.type;
		sType = sType.substring(sType.indexOf('/') + 1);
		if (sType.indexOf('+') != -1) {
			sType = sType.substring(0, sType.indexOf('+'));
		} else {
			sType = 'rss';
		}
		GM_setValue(iHistoryCount + '.href', oFeedInfo.href);
		GM_setValue(iHistoryCount + '.title', sFeedTitle);
		GM_setValue(iHistoryCount + '.homepage', oFeedInfo.homepage);
		GM_setValue(iHistoryCount + '.type', sType);
		GM_setValue('count', iHistoryCount + 1);
	}

	function clearHistory() {
		var iHistoryCount = getHistoryCount();
		for (var i = 0; i < iHistoryCount; i++) {
			GM_setValue(i + '.href', '');
			GM_setValue(i + '.title', '');
			GM_setValue(i + '.homepage', '');
			GM_setValue(i + '.type', '');
		}
		GM_setValue('count', 0);
	}

	function appendNew(elmRoot, elmParent, sNodeName) {
		var elmChild = elmRoot.createElement(sNodeName);
		elmParent.appendChild(elmChild);
		return elmChild;
	}

	function buildSubscriptionFile() {

		var oParser = new DOMParser();
		var elmRoot = oParser.parseFromString('<opml/>', 'application/xml');
		elmRoot.documentElement.setAttribute('version', '1.0');
		var nodeComment = elmRoot.createComment(
			'Save this using "File/Save Page As…", and then import it ' +
			'into your news aggregator.');
		elmRoot.documentElement.appendChild(nodeComment);
		var elmHead = appendNew(elmRoot, elmRoot.documentElement, 'head');
		var elmTitle = appendNew(elmRoot, elmHead, 'title');
		elmTitle.appendChild(elmRoot.createTextNode('Feed Collector'));
		var dateNow = new Date();
		var elmDate = appendNew(elmRoot, elmHead, 'dateCreated');
		elmDate.appendChild(elmRoot.createTextNode(dateNow.toGMTString()));
		var elmOwnerName = appendNew(elmRoot, elmHead, 'ownerName');
		var elmBody = appendNew(elmRoot, elmRoot.documentElement, 'body');
		var elmOutline = appendNew(elmRoot, elmBody, 'outline');
		elmOutline.setAttribute('title', 'Subscriptions');
		var iHistoryCount = getHistoryCount();
		var arFeeds = getAllHistoryItems();
		for (var i = 0; i < iHistoryCount; i++) {
			var oFeedInfo = arFeeds[i];
			var elmItem = appendNew(elmRoot, elmOutline, 'outline');
			elmItem.setAttribute('title', oFeedInfo.title);
			elmItem.setAttribute('htmlUrl', oFeedInfo.homepage);
			elmItem.setAttribute('type', oFeedInfo.type);
			elmItem.setAttribute('xmlUrl', oFeedInfo.href);
		}
		var serializer = new XMLSerializer();
		return serializer.serializeToString(elmRoot);
	}

	function displayFeeds(event) {
		var sSubscriptionData = buildSubscriptionFile();
		GM_openInTab('data:application/xml,'+ sSubscriptionData);
		event.preventDefault();
	}

	function clearFeeds(event) {
		var iHistoryCount = getHistoryCount();
		clearHistory();
		var elmFeedCollector = document.getElementById('feedcollector');
		if (elmFeedCollector) {
			elmFeedCollector.parentNode.removeChild(elmFeedCollector);
		}
		event.preventDefault()
	}

	String.prototype.trim = function() {
		var s = this;
		s = s.replace(/^\s+/, '');
		s = s.replace(/\s+$/, '');

		return s;
	}

	var arFeeds = getPageFeeds();
	for (var i = 0; i < arFeeds.length; i++) {
		addToHistory(arFeeds[i]);
	}
	var iHistoryCount = getHistoryCount();
	if (!iHistoryCount) { return; }
	var elmWrapper = document.createElement('div');
	elmWrapper.id = 'feedcollector';
	elmWrapper.innerHTML = '<div style="position: fixed; bottom: 0; ' +
		'right: 0; padding: 1px 4px 3px 4px; background-color: #ddd; ' +
		'color: #000; border-top: 1px solid #bbb; border-left: 1px ' +
		'solid #bbb; font-family: sans-serif; font-size: x-small;">' +
		'<a href="#" title="Display collected feeds" ' +
		'id="feedcollectordisplay" style="background-color: transparent; ' +
		'color: black; font-size: x-small; font-family: sans-serif; ' +
		'text-decoration: none;">' + iHistoryCount + ' feed' +
		(iHistoryCount > 1 ? 's' : '') + ' collected</a> &middot; ' +
		'[<a href="#" title="Clear list of collected feeds" ' +
		'id="feedcollectorclear" style="background-color: transparent; ' +
		'color: black; font-size: x-small; font-family: sans-serif; ' +
		'text-decoration: none;">clear</a>]</div>';
	document.body.insertBefore(elmWrapper, document.body.firstChild);
	document.getElementById('feedcollectordisplay').addEventListener(
		'click', displayFeeds, true);
	document.getElementById('feedcollectorclear').addEventListener(
		'click', clearFeeds, true);