Advanced Web Metrics

My standard word of caution - This is a tech tip and requires you to have a knowledge of html and javascript to implement and use it…

Following on from my previous post Tracking banners and other outgoing links automatically, this GA hack allows you to track downloads automatically. As you may know, tracking download files such as PDF, EXE, DOC and XLS can be achieved quite easily with the modification of the link to include an urchinTracker call to log a virtual pageview. However, as for tracking outgoing links, manually modifying each download link becomes inefficient when there are large numbers of ever changing files to track. You can overcome this by applying the JavaScript code below:

<script type="text/JavaScript">
// Only links written to the page (already in the DOM) will be tagged
// Script can be called multiple times

function addExtDocEvents() {
var as = document.getElementsByTagName("a");
var extDoc = [".doc",".xls",".exe",".zip",".pdf",".js"];
// add further document types as required

for(var i=0; i<as.length; i++) {
	var tmp = as[i].getAttribute("onclick");

// Tracking electronic documents - doc, xls, pdf, exe, zip
if (tmp != null && tmp.indexOf('urchinTracker') > -1) continue;
for (var j=0; j<extDoc.length; j++) {
if (as[i].href.indexOf(extTrack[0]) != -1 &&
as[i].href.indexOf(extDoc[j]) != -1) {
		var splitResult = as[i].href.split(extTrack[0]);
		as[i].setAttribute("onclick",((tmp != null) ? tmp : "") +
			"urchinTracker('/downloads" +splitResult[1]+ "');");
		break;
	}
}
}
}
addExtDocEvents()
</script>

The script works by looking for links within the browser’s Document Object Model (DOM) that match the file extension given in the variable array extDoc. If so it is modified to include the urchinTracker call. By this method, all file downloads will be reported as:

/downloads/the-url-that-is-clicked-on

Where the-url-that-is-on clicked on is minus ‘http://’. You can modify the JavaScript to adjust the path as required,

Tip: As for the Tracking of banners and other outgoing links, the position of this code within your page is important. This must placed after your call to the GATC. Alternatively place the addExtDocEvents() call in an onLoad event handler and host the JavaScript in a separate file.

A note on performance: Each time your page loads, this script will go through all links referenced on the page to see if it is for a download. Clearly the more links on your page, the harder the script must work. As long as the number of links on each page number in the hundreds and not thousands, performance should not be a problem. Also, pages with a large number of links, it is possible that visitors will click on a download link before the script has modified it. The result is that click through will not be tracked by Google Analytics.

I have combined both the Tracking of banners and other outgoing links - automatically with this hack into a single script that is available at: http://www.advanced-web-metrics.com/blog/scripts.

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