Thanks for that answer. You obviously know a lot about this issue. I guess they would be able to tell if the .js script file creates an a element with a specific href attribute and then add that element to a specific div tag after the page loads.
It sounds like it might be easier just to nofollow those links instead of going to all the trouble to redirect the .js file whenever Google Bot crawls the page. I fear that could be considered cloaking.
Another possibility would be a an alert that requires a user interaction before grabbing a url from a database. The user would click on the link without an href, the javascript onclick fires, the javascript grabs the the url from a database, the user is asked to click a button if they want to proceed, and then the user is redirected to the external url. That should keep the external URL out of the script code.