Javascript SEO Value
June 1, 2008 Posted by Al Castle

1 comment so far Categories: Castle, Marketing, SEO, Web Design & Dev Tags: google, javascript, SEO

It’s long been said that JavaScript had no search engine optimization value. A few months back while running through my web server logs I realized that Google, among a few other search engine bots were indexing files that were only referenced through Javascript.
I created a few tests to determine the extent of this. Each test has its own URL which allows me to determine which was actually called and from where.

[Note: These links are no longer active.]

Test-1: Ability to process basic code. In this test the variable bob if processed will be a complete URL. I explicitly did not call the document.write function. This code was in the index page.

Result: The result of this one was as expected. The URL was never assembled and thus not crawled.

Test-2: Ability to extract a fully qualified URL from a relative, externally referenced, Javascript file in the HTML head tags. The contents of the file as follows.

var taco;

function megataco()
{
	// are we good in a function?
	taco = 'http://blog.alcastle.com/_gb/search.php?h=listing.js';

	if( taco != null )
	{
		return taco.length;
	}
}

megataco();

Result: The externally referenced .js file was pulled and the URL contained within the function was indexed.

Test-3: Ability to crawl a fully qualified URL from the index page.

	var cran = 'http://blog.alcastle.com/_gb/search.php?h=index.php&t=literal';

Result: This test is not much different than the second, and likewise the results were the same.

Test-4 Crawling of a relative link from the index page.

     EditInPlace.defaults['save_url'] = ‘/tagline_save.php’;

        $(’editme’).editInPlace({
                auto_adjust: true,
                select_text: true
        });

Result: The relatively URL here was not crawled.

Conclusion: In looking around at various webmaster forums, I’ve found evidence that some have been aware of this for awhile. My own tests are perhaps half hazard, but they do prove that while the Javascript may not be processed by search bots, some bots can and do extract links from the page source. Providing the links contained within the Javascript are complete URLs, you can expect Google at least to crawl those referenced pages.