These links are not seen by the user and let the HTML file link to CSS files (used for styling) and JavaScript files (used to add interactive content).

JavaScript allows sites to customize links in different ways, but doing so may render the link unusable to crawlers. Here’s what Splitt recommends. Do: Keep it Straightforward ...

Google's John Mueller replied to a question around links found in JavaScript saying that once the link is rendered, Google will treat the link like how they treat any other link. John Mueller said ...

So if you want your links to be found, be safe and put them in standard html format. But if you don't want your links to be found, putting them in JavaScript or Flash won't guarantee that.

Always test your pages using Google’s own tools and third-party resources to view the rendered HTML to make sure all your content is showing up.