If your site utilizes Javascript based navigation, you are in for a treat. Google is now able to crawl links embedded in JavaScript onclick() events. These links will not only be followed by Google but they will also now pass both Page Rank and Anchor Text value!
What does this mean for your search results? If your site uses JavaScript links and is not optimized, then you just may see your rankings and site traffic increase in the very near future as your indexing improves.
On the other hand, if your site is well optimized chances are then you have already eliminated any JavaScript links, and your rankings will stay the same, for the most part. It is possible however, that if your competition ranking just beneath you previously managed to obtain their top ranking while using JavaScript links, their listings may jump up above yours with this update, and so as a result, your rankings could in theory drop slightly.
Regardless, it is great to see Google expanding its functionality when it comes to alternative forms of site navigation. JavaScript has been in use for a long time now and its surprising that it has taken this many years for Google to be able to follow it.
With all this being said, I don’t recommend going out and redesigning your site using JavaScript. When it comes to the other search engines as well as various mobile devices, JavaScript is still a poor choice. Stick with the HTML based text and image links for now wherever possible.